Color conversion films with plasmon enhanced fluorescent dyes

ABSTRACT

Color conversion films for a LCD (liquid crystal display) having RGB (red, green, blue) color filters, as well as such displays, formulations, precursors and methods are provided, which improve display performances with respect to color gamut, energy efficiency, materials and costs. The color conversion films absorb backlight illumination and convert the energy to green and/or red emission at high efficiency, specified wavelength ranges and narrow emission peaks. For example, rhodamine-based fluorescent compounds are used in matrices produced by sol gel processes and/or UV (ultraviolet) curing processes which are configured to stabilize the compounds and extend their lifetime—to provide the required emission specifications of the color conversion films. Film integration and display configurations further enhance the display performance with color conversion films utilizing various color conversion elements. Fluorescent emission may be enhanced by plasmon resonance of coupled nanoparticles.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.15/353,015, filed on Nov. 16, 2016, which claims the benefit of U.S.Provisional Application No. 62/255,857, filed on Nov. 16, 2015; and acontinuation-in-part of U.S. application Ser. No. 15/252,597, filed onAug. 31, 2016; and a continuation-in-part of U.S. application Ser. No.15/252,492, filed on Aug. 31, 2016, which claims the benefit of U.S.Provisional Application No. 62/255,853 filed on Nov. 16, 2015; all ofwhich are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to the field of color conversion films indisplays, and more particularly, to color conversion films withfluorescent compounds.

2. Discussion of Related Art

Improving displays with respect to their energy efficiency and colorgamut performance is an ongoing challenge in the industry. While colorconversion films are available which use quantum dots to enhance displayperformance, it is particularly challenging to achieve comparable goalsin ways that do not involve heavy metals such as toxic cadmium used inquantum dots.

SUMMARY OF THE INVENTION

The following is a simplified summary providing an initial understandingof the invention. The summary does not necessarily identify key elementsnor limit the scope of the invention, but merely serves as anintroduction to the following description.

One aspect of the present invention provides a color conversion film fora LCD (liquid crystal display) having RGB (red, green, blue) colorfilters, the color conversion film comprising color conversions elementsselected to absorb illumination from a backlight source of the LCD andhave at least one of a R emission peak and a G emission peak, wherein atleast some of the at least one RBF compound is electromagneticallycoupled to plasmon-resonant (PR) elements having a resonance spectrumthat at least partly overlap at least one of an absorption and anemission spectra of the at least one RBF compound.

These, additional, and/or other aspects and/or advantages of the presentinvention are set forth in the detailed description which follows;possibly inferable from the detailed description; and/or learnable bypractice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of embodiments of the invention and to showhow the same may be carried into effect, reference will now be made,purely by way of example, to the accompanying drawings in which likenumerals designate corresponding elements or sections throughout.

In the accompanying drawings:

FIG. 1 is a high level schematic overview illustration of disclosed filmproduction processes, film configurations and display configurations,according to some embodiments of the invention.

FIGS. 2A-2D and 3 are high level schematic illustrations ofconfigurations of digital displays with color conversion film(s),according to some embodiments of the invention.

FIG. 4 is an illustration example of polarization anisotropy of film(s)with RBF (rhodamine-based fluorescent) compound(s), according to someembodiments of the invention.

FIG. 5A is a high level schematic illustration of red (R) enhancement indevices with white illumination, according to some embodiments of theinvention.

FIG. 5B illustrates an example for the improvement in an RGB spectrumprovided by backlight unit using the film(s), according to someembodiments of the invention.

FIG. 6A is a high level schematic illustration of precursors,formulations, films and displays, according to some embodiments of theinvention. FIG. 6B illustrates schematically prior art methods accordingto Reisfeld 2006.

FIGS. 7A and 7B are examples for illustrations of characteristics offormulations and films, according to some embodiments of the invention.

FIGS. 8A-8E illustrate examples of emission results of films produced bysol gel processes, according to some embodiments of the invention.

FIG. 9 schematically illustrates some embodiments of PMMA(poly-methyl-methacrylate) cross-linked dyes, according to someembodiments of the invention.

FIG. 10-13 illustrate examples of emission results of films produced byUV curing processes, according to some embodiments of the invention.

FIG. 14 is a high level flowchart illustrating methods, according tosome embodiments of the invention.

FIGS. 15A and 15B are high level schematic illustrations fluorescentelements comprising RBF compounds coupled to plasmon-resonant (PR)elements, according to some embodiments of the invention.

FIG. 15C is a high level schematic spectrum illustration with absorptionand emission wavelengths of RBF compounds and related local surfaceplasmon resonance (LSPR) properties of various PR elements, according tosome embodiments of the invention.

FIG. 16 is a high level schematic illustration of a color conversionfilm having PR elements as coating of enclosure of RBF compoundsembedded in a matrix, according to some embodiments of the invention.

FIG. 17 is a high level schematic illustration of a color conversionfilm having PR elements as regular elements embedded in a film, to whichRBF compounds are coupled, according to some embodiments of theinvention.

FIG. 18 is a high level schematic illustration of a color conversionfilm having PR elements as regular perforations in a film, to which RBFcompounds are coupled, according to some embodiments of the invention.

FIG. 19 is a high level schematic illustration of fluorescent elementshaving PR elements as composite structures to which RBF compounds arecoupled, according to some embodiments of the invention.

FIG. 20 is a high level flowchart illustrating a method, according tosome embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the present inventionare described. For purposes of explanation, specific configurations anddetails are set forth in order to provide a thorough understanding ofthe present invention. However, it will also be apparent to one skilledin the art that the present invention may be practiced without thespecific details presented herein. Furthermore, well known features mayhave been omitted or simplified in order not to obscure the presentinvention. With specific reference to the drawings, it is stressed thatthe particulars shown are by way of example and for purposes ofillustrative discussion of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice.

Before at least one embodiment of the invention is explained in detail,it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention is applicable to other embodiments that may bepracticed or carried out in various ways as well as to combinations ofthe disclosed embodiments. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

Facing the challenge of improving the efficiency and color performanceof displays without having to rely on compounds involved in displayscontaining quantum-dot-based technologies (e.g., in color filters, colorconversion materials etc.), the inventors have discovered ways of usingorganic molecules to significantly improve display properties. In thefollowing, display configurations are presented with respect to the useof color conversion films and then sol-gel and UV (ultraviolet)technologies are disclosed for preparing color conversion films as wellas for preparing associated protective films or coatings for the colorconversion films.

Color conversion films for a LCD (liquid crystal display) having RGB(red, green, blue) color filters, as well as such displays,formulations, precursors and methods are provided, which improve displayperformances with respect to color gamut, energy efficiency, materialsand costs. The color conversion films absorb backlight illumination andconvert the energy to green and/or red emission at high efficiency,specified wavelength ranges and narrow emission peaks. For example,rhodamine-based fluorescent compounds are used in matrices produced bysol gel processes and/or UV (ultraviolet) curing processes which areconfigured to stabilize the compounds and extend their lifetime—toprovide the required emission specifications of the color conversionfilms. Film integration and display configurations further enhance thedisplay performance with color conversion films utilizing various colorconversion elements. Fluorescent emission may be enhanced by plasmonresonance of coupled nanoparticles.

FIG. 1 is a high level schematic overview illustration of disclosed filmproduction processes 100, film configurations 130 and displayconfigurations 140, according to some embodiments of the invention.Embodiments combine color conversion elements (such as rhodamine-basedfluorescent (RBF) compounds 115 and/or other color conversion elements116 such as fluorescent organic and/or inorganic compounds, quantum dotsetc.) into films 130 by various film production processes 100 (such assol gel processes 200, UV curing processes 300 and/or other processes101) to yield a variety of film configurations 130 such as colorconversion films 130 and/or protective films 131 (which may be alsocolor conversion films 130), which are then used in a variety of displayconfigurations 140. Films 130, 131 prepared by as sol gel processes 200and UV curing processes 300 may be combined to form film 130. Film(s)130 may be used in display(s) 140 in one or more ways, such as any of:positioned in one or more locations in a backlight unit 142 and/or inLCD panel 85 and used as multifunctional films 130 (e.g., configured tofunction as any of: color conversions films, protective films,diffusers, polarizers etc.). Further display configurations 140 maycomprise adjusting film(s) 130 according to the backlight source 135(see e.g., red enhancement below, possibly also green enhancement)and/or adjusting the display white point 145, adjustment which may becarried out by modifying any of the color conversion elements, filmproduction processes 100 and/or film configurations 130. Someembodiments provide integrative approaches to display configuration,which take into account multiple factors at all illustrated levels, asexemplified below.

Display Configurations

Film Positions

FIGS. 2A-2D and 3 are high level schematic illustrations ofconfigurations of digital display 140 with color conversion film(s) 130,according to some embodiments of the invention. Digital displays 140 areillustrated schematically as comprising a backlight unit 142 and a LCDpanel 85, the former providing RGB illumination 84A to the latter.Backlight unit 142 is illustrated schematically in FIG. 2A in anon-limiting manner as comprising a backlight source 80 (e.g., whiteLEDs 80B or blue LEDs 80A), a waveguide with reflector 82 (the latterfor side-lit waveguides), a diffuser 144, prism film(s) 146 (e.g.,brightness enhancement film (BEF), dual BDF (DBEF), etc.) and polarizerfilm(s) 148, which may be configured in various ways. Films 130 may beapplied at various positions in backlight unit 142 such as on eitherside (130A, 130B) of diffuser 144, on either side (130C, 130D) of atleast one of prism film(s) 146, on either side (130E, 130F) of at leastone polarizer film(s) 148, etc. In certain embodiments, film 120 may bedeposited on any of the film in back light unit 142.

In certain embodiments, films 130 may be used to replace diffuser 144and/or polarizer film 148 (and possibly prism film(s) 146), onceappropriate optical characteristics are provided in films 130 asexplained herein.

The location of film(s) 130 may be optimized with respect to radiationpropagation in backlight unit 142, in both forwards (84A) and backward(84B) directions due to reflections in backlight unit 142. For example,optimization considerations may comprise fluorescence efficiency, energyefficiency, stability of rhodamine-based fluorescent (RBF) compounds 115or other color conversion elements in film(s) 130, and so forth. As anon-limiting example, in the position of the lower film 130A, B (e.g.,on diffuser 144) more radiation is expected to excite RBF compounds115—increasing its conversion efficiency but increasing losses andreducing the durability of RBF compounds 115. In the position of thehigher film 130E, F (e.g., on polarizer film 148) less radiation isexpected to excite RBF compounds 115—reducing its conversion efficiencybut reducing losses and increasing the durability of RBF compounds 115and/or other color conversion elements in film(s) 130.

Some embodiments of displays 140 comprise a blue light source 80A (suchas blue LEDs—light emitting diodes) with film(s) 130 configured toprovide red and green components in RGB illumination 84A, e.g., by usingred-fluorescent RBF compound(s) (e.g., with silane precursor(s) such asPhTMOS (trimethoxyphenylsilane) and/or TMOS (trimethoxysilane) withfluorine substituents—see below) and green-fluorescent RBF compound(s)(e.g., with silane precursor(s) such as F₁TMOS(trimethoxy(3,3,3-trifluoropropyl)silane)—see below). It is emphasizedthat various silane precursor(s) 104 may be used with eitherred-fluorescent or green-fluorescent RBF compounds 115 as disclosedbelow.

The red and green fluorescent RBF compound(s) may be provided in asingle film layer 133 or in multiple film layers 134, 132. The processmay be optimize to provide required absorption and emissioncharacteristics of RBF compounds in film 130, while maintainingstability thereof during operation of display 140. Similarly, film(s)130 with other one or more color conversion elements (e.g., otherfluorescent compounds, organic or inorganic, quantum dots etc.) may beintegrated in display 140 in a similar way an according to respectiveconsiderations. In the following any of the mentioned RBF compound(s)may, in some embodiments, be replaced or augmented by other colorconversion elements (e.g., other fluorescent compounds, organic orinorganic, quantum dots etc.).

Some embodiments of displays 140 comprise a white light source 80B (suchas white LEDs) with film(s) 130 configured to provide red and greencomponents in RGB illumination 84A, e.g., by using red-fluorescent RBFcompound(s) (e.g., with PhTMOS and/or TMOS with fluorine substituents assilane precursor(s)). The red fluorescent RBF compound(s) may beprovided in a single film layer or in multiple film layers 134. Theprocess may be optimize to provide required absorption and emissioncharacteristics of RBF compounds in film 130, while maintainingstability thereof during operation of display 140. Red-fluorescent RBFcompound(s) may be used to shift some of the yellow region in theemission spectrum of white light source 80B into the red region, toreduce illumination losses in LCD panel 85 while maintaining the balancebetween B and R+G in RGB illumination 84A.

FIG. 2B illustrates in more details various films and elements indisplay 140 to which film 130 may be associated or which may be replacedby film 130 in some embodiments. LCD panel 85 is shown to includecompensation films 85A, 85H, glass layers 85B, 85G, thin filmtransistors (TFT) 85C, ITO (indium tin oxide) layers 85D, 85F, liquidcrystal cell (LC) 85E, RGB color filters 86, polarizer film 85I andprotective film 85J (e.g., anti-glare, anti-reflection). FIG. 2B furtherillustrates typical illumination transmission in each layer andcumulatively, indicating ca. 40% loss in backlight unit 142 and 90% lossin LCD panel 85, the latter mainly resulting from RGB color filters 86and polarizers 84A in LCD panel 85 and backlight unit 142. One or morefilm(s) 130 may be attached to or replace any of various layers inbacklight unit 142 and/or in LCD panel 85, depending on considerationsof minimizing further illumination losses, film performance and lifetimeof the fluorescent dyes (RBF compounds 115). As non-limiting examples,FIG. 2B illustrates schematically associating on or more films 130 withany of diffuser 144A and/or light guide 82, prism layer(s) 146, diffuser144B, polarizer 84A (in either or both backlight unit 142 and LCD panel85), LC 85E, ITO 85F and/or color filters 86. It is emphasized that FIG.2B merely provides a non-limiting example of a display configuration,and films 130 may be applied at various positions and any displayconfiguration.

In some embodiments, similar considerations may be used with respect topositioning of any type of color conversion film 130, which may comprisecolor conversion elements other than RBF compounds 115, such as organic(non-rhodamine-based) or inorganic fluorescent compounds, quantum dotsetc. Various display 140 configurations may be provided, which optimizeillumination loss with film parameters and lifetime of the colorconverting elements.

FIG. 2D illustrates and example for configuration of film 130 foldedinto a zig-zag form, characterized by an overall length L, overallthickness d₁ and step d₂ between folds. Film 130 may be folded toincrease the film thickness through which the illumination passes,without increasing the actual thickness of film 130 (formulatedotherwise—to reduce the light flux per area of film 130). The foldingmay increase the lifetime of RBF compounds 115 in film or of any othercomprise color conversion elements on which film 130 may be based, suchas organic (non-rhodamine-based) or inorganic fluorescent compounds,quantum dots etc.

FIG. 2C schematically illustrates some of the above considerations, bycomparing display 140B with color conversion film 130 in LCD panel 85versus display 140A with color conversion film 130 in backlight unit142. The schematic illustrations depict the illumination intensity asI₀, and illumination components R, G, B as they are produced in therespective display. In display 140A, color conversion film 130 inbacklight unit 142 provides illumination at RGB, assuming in anon-limiting manner no loss on the conversion. In LCD panel 85, colorfilters 86 remove two of the three illumination components, leaving ca.10% of the original illumination at each color component (see also FIG.2B, illustrating a more realistic lower rate of less than 5% per colorcomponent). When placing color conversion film 130 in LCD panel 85(e.g., as a patterned film 130), as illustrated for display 140B(assuming blue LED illumination), a blue component may be delivereddirectly to blue color filter 86 without color conversion or filtering,while R and G may be converted from corresponding blue component justbefore filters 86, so that that filters 86 pass most or all of theillumination they receive, which is wavelength-adjusted just beforeentering color filters 86—resulting in a much higher efficiency than indisplay 140A of ca. 30% of the original illumination at each colorcomponent (corresponding to 10-15% per color component in terms of FIG.2B).

Such gain in efficiency may be achieved by some embodiments having anytype of color conversion film 130, which may comprise color conversionelements other than RBF compounds 115, such as organic(non-rhodamine-based) or inorganic fluorescent compounds, quantum dotsetc. Various display configurations may be provided which increaseillumination use efficiency by positioning respective color conversionfilm 130 in LCD panel 85, before color filters 86. Some embodimentscomprise respective LCD panels 85 having color conversion film 130integrated therein and positioned before color filters 86 thereof, aswell as corresponding displays 140.

FIG. 3 schematically illustrates white point adjustment 145 that extendsa display lifetime of display 140, according to some embodiments of theinvention. Illustration 145A shows an example for EC-154 (Z₃ withJK-71+Z₂ with ES-61, see line 9 in Table 1 below) sample color gamutcompared to DCI (digital cinema initiatives) P3 cinema standard colorgamut over the CIE 1931 color space with a white region indicated by WRand a white point denoted by WP, having a diameter which is denoted by dand may be e.g., 0.01 in the diagram's x coordinates. The region WPdenotes the range within which display 140 is considered to be withinthe specifications with respect to its color performance. Once theactual white point of display 140 is outside region WP, even when itremains within a possibly larger region WR corresponding to white color,display 140 is considered over its lifetime and not operating accordingto specifications. In a typical setting, films 130 are configured toprovide a white point 141A at the center of the region WP and as withtime RBF compounds 115 or other color conversion elements degrade 141(indicated in graph 145C showing the emission spectrum of film 130 byarrows which are denoted Time) white point 141A moves until it exitsregion WP and the display is considered over its lifetime. Thedegradation in terms of the distance on color diagram 145A isillustrated in graph 145B using non-limiting experimental data of thedistance from point 141A over the operation time (in arbitrary units,a.u., scaled to 1000) of the display. In some embodiments of display 140however, film(s) 130 may be fine-tuned to have the exact white pointwithin region WP but at a point 141B on the edge of it which is oppositeto the direction of degradation marked by arrow 141 (illustrations 145D,145E show an enlarged view of white region WR). Such fine tuning towhite point 141A enables the display characteristics to be changed toca. double as much as with white point 141A while staying within thespecified region WP, and as a result ca. double the lifetime of display140. The semi-quantitative example in graph 145B illustrates an increasein display lifetime, from ca. 600 a.u. to ca. 900 a.u., when changingthe white-point from 141A to 141B. As a result of the change, instead ofdisplay starting exactly white and becoming somewhat colder white (seegraph 145C, the green and red components decrease with time andcorrespondingly the blue component increases), display 140 starts a bitwarmer, goes through the exact white point and ends a bit colder, with alonger lifetime overall. Setting a higher concentration of RBF compounds115 or other color conversion elements in film 130 thus enableseffective lengthening of the lifetime of display 140. Examples forincreased dye concentrations may be up to 20% for green dyes and up to40% for red dyes. Some embodiments comprising raising the concentrationof one or more types of dyes (such as red-fluorescent andgreen-fluorescent RBF compounds 115), to fine tune the exact white pointof display 140. The increased concentration of dyes may result in asomewhat warmer white within specified region WP. Illustrations 145D and145E emphasize that white point 141B may be selected according to knowndegradation 141 of color conversion film 130 with respect to specifiedwhite point WP, for any type of film 130, including films using organic(non-rhodamine-based) or inorganic fluorescent compounds, quantum dotsetc.

Polarization

Film 130 may comprise at least one layer 134 with red fluorescent RBFcompound, or at least one layer 134 with red fluorescent RBF compoundand thereupon at least one layer 132 with green fluorescent RBFcompound. At least one of the layers of film 130 may be configured toexhibit polarization properties.

FIG. 4 is an illustration example of polarization anisotropy of film(s)130 with RBF compound(s) 115, according to some embodiments of theinvention. The inventors have found out that in certain cases, duringthe embedding of RBF compound(s) 115 in film 130, the moleculesself-assemble to affect light polarization, providing at least partiallypolarized light emission. Process parameters may be adjusted to enhancethe degree of polarization of light emitted from film 130, e.g., byproviding conditions that cause self-assembly to occur to a largerextent. Without being bound by theory, the inventors suggest that thepolarized emission of fluorescence is related to the limitations onrotational motions of the macromolecular fluorophores during thelifetime of the excitation state (limitations relating to their size,shape, degree of aggregation and binding, and local environmentparameters such as solvent, local viscosity and phase transition). Theinventors have further found out that these limitations may be at leastpartially controlled by the preparation process of film 130 which maythus be used to enhance illumination polarization in display 140.

For example, FIG. 4 illustrates polarization and anisotropy measurementof films 130 prepared with red and green fluorescent compounds(specifically, green coumarin 6 dye and rhodamine 101 red moleculardyes, using the sol gel process). In the example, the anisotropy valuesrange between 0.3-0.5 at the emission wavelengths.

Films 130 having different red and/or green fluorescent RBF compound115, as well as films 130 prepared by UV curing also presentpolarization properties and may be used in device 140 to enhance or atleast partially replace polarizer films (e.g., 84A, 85I etc. see FIGS.2A and 2B).

Some embodiments comprise any type of color conversion film 130, whichmay comprise color conversion elements other than RBF compounds 115,such as organic (non-rhodamine-based) or inorganic fluorescentcompounds, quantum dots etc.—configured to provide polarize fluorescentradiation as disclosed above. Such films 130 may be used to enhance orat least partially replace polarizer films in respective displays 140.

Red Enhancement

FIG. 5A is a high level schematic illustration of red (R) enhancement indevices with white illumination, according to some embodiments of theinvention. FIG. 5A schematically illustrates a typical white lightspectrum 80B-1 (of white illumination source 80B), optimized to provideRGB illumination 84A in prior art backlight units, and typical ranges(85R, 85G, 85B) of RGB filters 86 in LCD panel 85 (see FIGS. 2B and 2C).The inventors have noticed that while white light spectrum 80B-1 isoptimized with respect to the ratio between its blue section (80B-B) andits yellow section (80B-Y), it is deficient with respect to the relativeposition of the yellow region (80B-Y) and G and R ranges 85G, 85R,respectively (corresponding, for example, to B, G, R denoted in FIG.2C). Indeed, much of the illumination energy in yellow region 80B-Y isfiltered out and thus wasted in the operation of the display andmoreover, color cross talk (part of the yellow orange might go to thegreen filter and some of the green-yellow to the red filter) whichdegrades the color gamut. The inventors have further found out thatusing film(s) 130 with red-fluorescent RBF compound(s) 115 (layer(s)134) shifts 132A at least some of the illumination energy in yellowregion 80B-Y into red region 85R which is passed by the R (red) filterin LCD panel 85, and is therefore not wasted. Using film(s) 130 thusincreases the energy efficiency of display 140 and possibly improves itscolor gamut.

FIG. 5B illustrates an example for the improvement in RGB spectrum 84Bprovided by backlight unit 84 using film(s) 130, according to someembodiments of the invention. In this specific non-limiting example,films 130 were produced by UV curing process 300. White light spectrum80B-1 is somewhat different from the one illustrated in FIG. 5A due tothe difference in white light source 80B, yet also exhibits a peak inthe yellow region. In contrast, emission spectrum 134-1 of film 130(made of layer(s) 134—specifically—one to three layers with JK32(0.02-0.3 mg/ml for each layer, spectra shown without LCD color filtereffects) in backlight unit 142 splits the yellow peak of white lightspectrum 80B-1 into a green and a red peak, each within the range of thecorresponding G and R filters, thereby increasing the efficiency,reducing the color cross talk and improving the gamut of display 140,e.g., by providing a more saturated (narrower FWHM, full width at halfmaximum) red and at longer red wavelength. In the example, thecharacteristics of the green and red peaks of emission spectrum 134-1 offilm 130 were 618±5 nm peak with FWHM of ca. 60 nm for the red peak and518±5 nm peak with FWHM of ca. 50 nm for the green peak; with thequantum yield of film 130 being between 70-90% and the lifetime atdevice level being between 20,000-50,000 hour for multiple repeats.

Some embodiments comprise any type of color conversion film 130, whichmay comprise color conversion elements other than RBF compounds 115,such as organic (non-rhodamine-based) or inorganic fluorescentcompounds, quantum dots etc.—configured to provide polarize fluorescentradiation as disclosed above. Such films 130 may be used to RGB spectra84B by providing shifts 132A of yellow illumination 80B-Y into the redregion of corresponding R color filters 86 in respective displays 140.

In some embodiments, films 130 may be configured to provide greenenhancement, using only or mostly green-fluorescent compounds.

Rhodamine-Based Fluorescent Molecules

A wide range of fluorescent organic molecules may be incorporated infilms 130, such as materials of the xanthene dye family likefluorescein, rhodamine derivatives and coumarin family dyes, as well asvarious inorganic fluorescent materials. In the following, explicitexamples of rhodamine-based derivatives, RBF compounds 115, arepresented in detail, in a non-limiting manner.

Red-Fluorescent RBF Compounds

Some embodiments of red-fluorescent RBF compounds 115 are defined byFormula 1.

wherein

-   R¹ is COOR, NO₂, COR, COSR, CO(N-heterocycle), CON(R)₂, or CN;-   R² each is independently selected from H, halide, N(R)₂, COR, CN,    CON(R)₂, CO(N-heterocycle), NCO, NCS, OR, SR, SO₃H, SO₃M and COOR;-   R³ each is independently selected from H, halide, N(R)₂, COR, CN,    CON(R)₂, CO(N-heterocycle), NCO, NCS, OR, SR, SO₃H, SO₃M and COOR;-   R⁴-R¹⁶ and R^(4′)-R^(16′) are each independently selected from H,    CF3, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, alkenyl,    alkynyl, aryl, benzyl, halide, NO₂, OR, N(R)₂, COR, CN, CON(R)₂,    CO(N-Heterocycle) and COOR;-   R is H, alkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl,    benzyl, —(CH₂CH₂O)_(r)CH₂CH₂OH,    —(CH₂)_(p)OC(O)NH(CH₂)_(q)Si(Oalkyl)₃, —(CH₂)_(p)OC(O)CH═CH₂ or    —(CH₂)_(p)Si(Oalkyl)₃;-   n and m is each independently an integer between 1-4;-   p and q are each independently an integer between 1-6;-   r is an integer between 0-10;-   M is a monovalent cation; and-   X is an anion.

The positions of R¹, (R²)_(n) and (R³)_(m) may be selected to be anyfeasible position with respect to the indicated ring. Any of R¹,(R²)_(n) and (R³)_(m) may be positioned at ortho, meta or para positionswith respect to the rest of the molecule, as long as the resultingstructure is chemically feasible. Precursors 110 and formulation 120 maybe adapted to accommodate and support embodiments of the selectedred-fluorescent RBF compound(s) according to the principles disclosedherein.

Specific, non-limiting, examples of red-fluorescent RBF compounds 115which were tested below include compounds denoted ES61, JK32 (shown asJK-32A and/or JK-32B), RS56 (shown as RS56A and/or RS56B), RS106 andRS130.

Some embodiments of red-fluorescent RBF compounds are presented in moredetail in U.S. patent application Ser. No. 15/252,492 and are consideredlikewise part of the present disclosure. Non-limiting examples areprovided in the following variants, numbered 1-1, 1-2, 1-3, 1-4, 1-5,1-6, 1-7, 1-8, 1-9, 1-10, 1-11, 1-9A, 1-10a and 1-11a.

Green-Fluorescent RBF Compounds

Some embodiments of green-fluorescent RBF compounds are defined byFormulas 2 and 3.

Wherein:

-   R¹ each is independently H, Q¹, OQ¹, CF₃, C(O)Q¹, NQ¹Q², NO₂, CN,    SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS, —OC(O)OQ¹ or halide;-   R² each is independently H, Q¹, OQ¹, CF₃, C(O)Q¹, NQ¹Q², NO₂, CN,    SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS, —OC(O)OQ¹ or halide;-   R³ each is independently H, Q¹, OQ¹, CF₃, C(O)Q¹, NQ¹Q², NO₂, CN,    SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS, —OC(O)OQ¹ or halide;-   R⁴, R^(4′), R⁸ and R^(8′) are each independently selected from H,    alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl and benzyl;-   R⁵ and R^(5′) are each independently selected from Z, OQ¹, CF₃,    C(O)Q¹, COOQ¹, CON(Q¹)₂, NQ¹Q², NO₂, CN, SO₃ ⁻, SO₃M, SO₃H, SQ¹,    —NQ¹Q²CONQ³Q⁴, NCO, NCS, alkenyl, alkynyl, epoxide, alkylated    epoxide, azide and halide;-   R⁶, R^(6′), R⁷ and R^(7′) are each independently selected from H,    Q¹, OQ¹, CF₃, C(O)Q¹, COOQ¹, CON(Q¹)₂, NQ¹Q², NO₂, CN, SO₃ ⁻, SO₃M,    SO₃H, SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS, alkenyl, alkynyl, epoxide,    alkylated epoxide, azide and halide; or-   R⁴ and R⁵ or R^(4′) and R^(5′) form together a N-heterocyclic ring    wherein said ring is optionally substituted;-   Q¹ and Q² are each independently selected from H, alkyl, haloalkyl,    heterocycloalkyl, cycloalkyl, aryl, benzyl,    —(CH₂)_(p)OC(O)NH(CH₂)_(p)Si(Oalkyl)₃, —(CH₂)_(p)OC(O)CH═CH₂,    —(CH₂)_(p)Si(Oalkyl)₃, —OC(O)N(H)Q⁴, —OC(S)N(H)Q⁴, —N(H)C(O)N(Q³)₂    and —N(H)C(S)N(Q³)₂;-   Z is selected from alkyl, haloalkyl, heterocycloalkyl, cycloalkyl,    aryl, benzyl, —(CH₂)_(p)OC(O)NH(CH₂)_(p)Si(Oalkyl)₃,    —(CH₂)_(p)OC(O)CH═CH₂, —(CH₂)_(p)Si(Oalkyl)₃, —OC(O)N(H)Q⁴,    —OC(S)N(H)Q⁴, —N(H)C(O)N(Q³)₂ and —N(H)C(S)N(Q³)₂;-   Q³ and Q⁴ are each independently selected from H, alkyl, haloalkyl,    heterocycloalkyl, cycloalkyl, aryl and benzyl;-   M is a monovalent cation;-   n, m and l are independently an integer between 1-5;-   p and q are independently an integer between 1-6; and-   X is an anion;

wherein

-   T¹ each is independently H, Q¹, OQ¹, CF₃, C(O)Q¹, NQ¹Q², NO₂, CN,    SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS, —OC(O)OQ¹ or halide;-   T² each is independently H, Q¹, OQ¹, CF₃, C(O)Q¹, NQ¹Q², NO₂, CN,    SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS, —OC(O)OQ¹ or halide;-   T³ each is independently H, Q¹, OQ¹, CF₃, C(O)Q¹, NQ¹Q², NO₂, CN,    SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS, —OC(O)OQ¹ or halide;-   T⁴ and T^(4′) are each independently selected from alkyl, haloalkyl,    heterocycloalkyl, cycloalkyl, aryl and benzyl;-   T⁵ and T^(5′) are each independently selected from H, Q¹, OQ¹, CF₃,    C(O)Q¹, COOQ¹, CON(Q¹)₂, NQ¹Q², NO₂, CN, SO₃ ⁻, SO₃M, SO₃H, SQ¹,    —NQ¹Q²CONQ³Q⁴, NCO, NCS, alkenyl, alkynyl, epoxide, alkylated    epoxide, azide and halide;-   T⁶, T^(6′), T⁷ and T^(7′) are each independently selected from H,    Q¹, OQ¹, CF₃, C(O)Q¹, COOQ¹, CON(Q¹)₂, NQ¹Q², NO₂, CN, SO₃ ⁻, SO₃M,    SO₃H, SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS, alkenyl, alkynyl, epoxide,    alkylated epoxide, azide and halide; or-   T⁴ and T⁵ or T^(4′) and T^(5′) form together a N-heterocyclic ring    wherein said ring is optionally substituted;-   Q¹ and Q² are each independently selected from H, alkyl, haloalkyl,    heterocycloalkyl, cycloalkyl, aryl, benzyl,    —(CH₂)_(p)OC(O)NH(CH₂)_(p)Si(Oalkyl)₃, —(CH₂)_(p)OC(O)CH═CH₂,    —(CH₂)_(p)Si(Oalkyl)₃, —OC(O)N(H)Q⁴, —OC(S)N(H)Q⁴, —N(H)C(O)N(Q³)₂    and —N(H)C(S)N(Q³)₂;-   Q³ and Q⁴ are each independently selected from H, alkyl, haloalkyl,    heterocycloalkyl, cycloalkyl, aryl and benzyl;-   M is a monovalent cation;-   n, m and l are independently an integer between 1-5;-   p and q are independently an integer between 1-6; and-   X is an anion.

The positions of (R¹)_(m), (R²)_(n) and (R³)_(l) and of (T¹)_(m),(T²)_(n) and (T³)_(l) may be selected to be any feasible position withrespect to the indicated ring. Any of (R¹)_(m), (R²)_(n) and (R³)_(l)and any of (T¹)_(m), (T²)_(n) and (T³)_(l) may be positioned at ortho,meta or para positions with respect to the rest of the molecule, as longas the resulting structure is chemically feasible. Precursors 110 andformulation 120 may be adapted to accommodate and support embodiments ofthe selected green-fluorescent RBF compound(s) according to theprinciples disclosed herein.

Some embodiments of green-fluorescent RBF compounds are defined byFormula 4.

wherein:

-   -   R¹ each is independently H, Q¹, OQ¹, CF₃, C(O)OQ¹, C(O)NQ¹Q²,        NHC(O)Q¹, C(O)Q¹, NQ¹Q², NO₂, CN, SQ¹, —NQ¹Q²CONQ³Q⁴, NCO, NCS,        —OC(O)OQ¹, SO₃—, SO₃Q¹, or halide;

-   n is an integer between 1-5;

-   R³, R^(3′), R⁶ and R^(6′) are each independently selected from H,    CF₃, alkyl, alkenyl, alkynyl, haloalkyl, heterocycloalkyl,    cycloalkyl, aryl and benzyl;

-   R², R^(2′), R⁴, R4′, R⁵ and R^(5′) are each independently selected    from H, Q¹, OQ¹, CF₃, NQ¹Q², NO₂, CN, SO₃ ⁻, SO₃Q¹ and halide;

-   Q¹ and Q² are each independently selected from H, substituted or    unsubstituted alkyl, substituted or unsubstituted alkenyl,    substituted or unsubstituted alkynyl, azide, haloalkyl,    heterocycloalkyl, cycloalkyl, aryl, benzyl,    —(CH₂)_(p)OC(O)NH(CH₂)_(q)Si(Oalkyl)₃, —(CH₂)_(p)OC(O)CH═CH₂,    —(CH₂)_(p)Si(Oalkyl)₃, —OC(O)N(H)Q⁴, —OC(S)N(H)Q⁴, —N(H)C(O)N(Q³)₂    and —N(H)C(S)N(Q³)₂;

-   Q³ and Q⁴ are each independently selected from H, alkyl, haloalkyl,    heterocycloalkyl, cycloalkyl, aryl and benzyl;

-   X is an anion.

An “alkyl” group refers, in one embodiment, to a saturated aliphatichydrocarbon, including straight-chain or branched-chain. In oneembodiment, the alkyl group has 1-20 carbons. In another embodiment, thealkyl group has 1-8 carbons. In another embodiment, the alkyl group has1-7 carbons. In another embodiment, the alkyl group has 1-6 carbons. Nonlimiting examples of alkyl groups include methyl, ethyl, propyl,isobutyl, butyl, pentyl or hexyl. In another embodiment, the alkyl grouphas 1-4 carbons. In another embodiment, the alkyl group may beoptionally substituted by one or more groups selected from halide,hydroxy, alkoxy, carboxylic acid, aldehyde, carbonyl, amido, cyano,nitro, amino, alkenyl, alkynyl, aryl, azide, epoxide, ester, acylchloride and thiol.

A “cycloalkyl” group refers, in one embodiment, to a ring structurecomprising carbon atoms as ring atoms, which are saturated, substitutedor unsubstituted. In another embodiment the cycloalkyl is a 3-12membered ring. In another embodiment the cycloalkyl is a 6 memberedring. In another embodiment the cycloalkyl is a 5-7 membered ring. Inanother embodiment the cycloalkyl is a 3-8 membered ring. In anotherembodiment, the cycloalkyl group may be unsubstituted or substituted bya halide, alkyl, haloalkyl, hydroxyl, alkoxy, carbonyl, amido,alkylamido, dialkylamido, cyano, nitro, CO₂H, amino, alkylamino,dialkylamino, carboxyl, thio and/or thioalkyl. In another embodiment,the cycloalkyl ring may be fused to another saturated or unsaturated 3-8membered ring. In another embodiment, the cycloalkyl ring is anunsaturated ring. Non limiting examples of a cycloalkyl group comprisecyclohexyl, cyclohexenyl, cyclopropyl, cyclopropenyl, cyclopentyl,cyclopentenyl, cyclobutyl, cyclobutenyl, cycloctyl, cycloctadienyl(COD), cycloctaene (COE) etc.

A “heterocycloalkyl” group refers in one embodiment, to a ring structureof a cycloalkyl as described herein comprising in addition to carbonatoms, sulfur, oxygen, nitrogen or any combination thereof, as part ofthe ring. In one embodiment, non-limiting examples of heterocycloalkylinclude pyrrolidine, pyrrole, tetrahydrofuran, furan, thiolane,thiophene, imidazole, pyrazole, pyrazolidine, oxazolidine, oxazole,isoxazole, thiazole, isothiazole, thiazolidine, dioxolane, dithiolane,triazole, furazan, oxadiazole, thiadiazole, dithiazole, tetrazole,piperidine, oxane, epoxide, thiane, pyridine, pyran, thiopyran,piperazine, morpholine, thiomorpholine, dioxane, dithiane, diazine,oxazine, thiazine, dioxine, triazine, and trioxane.

As used herein, the term “aryl” refers to any aromatic ring that isdirectly bonded to another group and can be either substituted orunsubstituted. The aryl group can be a sole substituent, or the arylgroup can be a component of a larger substituent, such as in anarylalkyl, arylamino, arylamido, etc. Exemplary aryl groups include,without limitation, phenyl, tolyl, xylyl, furanyl, naphthyl, pyridinyl,pyrimidinyl, pyridazinyl, pyrazinyl, triazinyl, thiazolyl, oxazolyl,isooxazolyl, pyrazolyl, imidazolyl, thiophene-yl, pyrrolyl,phenylmethyl, phenylethyl, phenylamino, phenylamido, etc. Substitutionsinclude but are not limited to: F, Cl, Br, I, C₁-C₅ linear or branchedalkyl, C₁-C₅ linear or branched haloalkyl, C₁-C₅ linear or branchedalkoxy, C₁-C₅ linear or branched haloalkoxy, aryl, heterocycloalkyl,CF₃, CN, NO₂, —CH₂CN, NH₂, NH-alkyl, N(alkyl)₂, hydroxyl, —OC(O)CF₃,—OCH₂Ph, —NHCO-alkyl, COOH, —C(O)Ph, C(O)O-alkyl, C(O)H, or — or—C(O)NH₂.

In one embodiment, the term “halide” used herein refers to anysubstituent of the halogen group (group 17). In another embodiment,halide is flouride, chloride, bromide or iodide. In another embodiment,halide is fluoride. In another embodiment, halide is chloride. Inanother embodiment, halide is bromide. In another embodiment, halide isiodide.

In one embodiment, the term haloalkyl used herein refers to alkyl, orcycloalkyl substituted with one or more halide atoms. In anotherembodiment haloalkyl is perhalogenated (completely halogenated, no C—Hbonds). In another embodiment, haloalkyl is CH₂CF₃. In anotherembodiment. haloalkyl is CH₂CCl₃. In another embodiment, haloalkyl isCH₂CBr₃. In another embodiment, haloalkyl is CH₂CI₃. In anotherembodiment, haloalkyl is CF₂CF₃. In another embodiment, haloalkyl isCH₂CH₂CF₃. In another embodiment, haloalkyl is CH₂CF₂CF₃. In anotherembodiment, haloalkyl is CF₂CF₂CF₃.

A specific, non-limiting, example of green-fluorescent RBF compounds 115which were tested below include compounds denoted JK-71.

Some embodiments of green-fluorescent RBF compounds are presented inmore detail in U.S. patent application Ser. No. 15/252,597 and areconsidered likewise part of the present disclosure. Non-limitingexamples are provided in the following variants, numbered 2-8, 2-9,2-10, 2-11, 2-12, 2-15 and 2-16.

Referring back to FIGS. 1 and 2A, some embodiments comprise colorconversion films 130 for LCD's 140 having RGB color filters 86 whichcomprise color conversion element(s) such as RBF compound(s) 115 orother compounds 116 selected to absorb illumination from backlightsource 80 of LCD 140 and have a R emission peak and/or a G emission peak(see non-limiting examples below). For example, color conversion films130 for LCD's with backlight source 80 providing blue illumination maycomprise both R and G peaks provided by corresponding RBF compoundshaving Formula 1 and Formula 2. In another example, color conversionfilms 130 for LCD's with backlight source 80 providing whiteillumination may comprise R peak provided by corresponding RBFcompound(s) having Formula 1. Color conversion film(s) 130 may be set ineither or both backlight unit 142 and LCD panel 85; and may be attachedto other film(s) in LCD 140 or replace other film(s) in LCD 140, e.g.being multifunctional as both color conversion films and polarizers,diffusers, etc., as demonstrated above. Color conversion film(s) 130 maybe produced by various methods, such as sol gel and/or UV curingprocesses, may include respective dyes at the same or different layers,and may be protected by any of a protective film, a protective coatingand/or protective components in the respective sol gel or UV curedmatrices which may convey enhanced flexibility, mechanical strengthand/or less susceptibility to humidity and cracking. Color conversionfilm(s) 130 may comprise various color conversion elements such asorganic or inorganic fluorescent molecules, quantum dots and so forth.

Sol-Gel Processes

Some embodiments of fluorescent film production 100 were developed onthe basis of sol gel technology in a different field of laser dyes.Reisfeld 2006 (Doped polymeric systems produced by sol-gel technology:optical properties and potential industrial applications, Polimery 2006,51(2): 95-103) reviews sol-gel technology based on hydrolysis andsubsequent polycondensation of precursors, such as organo-siliconalkoxides, leading to formation of amorphous and porous glass. Thematrices for incorporation of organically active dopants are theglass/polymer composites, organically modified silicates (ORMOSIL) orhybrid materials zirconia-silica-polyurethane (ZSUR). However, thematrices taught by Reisfeld 2006 do not yield films with photo-stablefluorescent compounds that are necessary for color conversion films.

Starting from Reisfeld 2006, the inventors have found out that sol geltechnology may be modified and adapted for producing films offluorescent optical compounds which may be used in displays, withsurprisingly good performance with respect to emission spectra andstability of the fluorescent compounds. The inventors have found outthat multiple modifications to technologies discussed in Reisfeld 2006enable using them in a completely different field of implementation andmoreover, enable to enhance the stability of the fluorescent compoundsand to tune their emission spectra (e.g., peak wavelengths and widths ofpeaks to enable wide color gamut illuminance from the display backlight)using process parameters. Hybrid sol-gel precursor formulations,formulations with rhodamine-based fluorescent compounds, films, displaysand methods are provided, in which the fluorescent compounds arestabilized and tuned to modify display backlight illumination in amanner that increases the display's efficiency and widens its colorgamut. Silane precursors are used with silica nanoparticles and zirconiato provide fluorescent films that may be applied in various ways in thebacklight unit and/or in the LCD panel and improve the display'sperformance. The sol-gel precursor and film forming procedures may beoptimized and adjusted to provide a high photostability of thefluorescent compounds and narrow emission peaks of the backlight unit.

FIG. 6A is a high level schematic illustration of precursors 110,formulations 120, films 130 and displays 140 according to someembodiments of the invention. FIG. 6B illustrates schematically priorart methods 90 according to Reisfeld 2006. Disclosed processes andmethods 200 overarch compounds and processing steps for formulations110, 120 and film 130 as well as integration steps of films 130 indisplay 140.

Hybrid sol-gel precursor formulations 110 comprise an ESOR 106 preparedfrom TEOS (tetraethyl orthosilicate) 102, at least one silane precursor104 and/or MTMOS (methyltrimethoxysilane) 91B, and GLYMO 91C; a DURSpowder 109 prepared from isocyanate-functionalized silica nanoparticles94B and ethylene glycol 108; and a transition metal(s) alkoxide matrixsolution 103 (based on e.g., zirconia, titania or other transitionmetal(s) alkoxides). The ratios (wt/vol/vol (mg/ml/ml)) ofDURS/ESOR/transition metal(s) alkoxide matrix solution may be in therange 15-25/1-3/1, with each of the components possibly deviating by upto 50% from the stated proportions. Additional variants 107 are providedbelow; FIG. 6A presents non-limiting examples of process 200.

In a non-limiting example, the ESOR and the transition metal(s) alkoxidematrix solution may be mixed at ratio of between 1:1 and 3:1 (e.g., 2:1)followed by adding the DURS at a concentration of 5-10 mg/1 ml mixed(e.g., ESOR and zirconia) solution—resulting in ratios (wt/vol/vol(mg/ml/ml)) of DURS/ESOR/transition metal(s) alkoxide matrix solution of15-30/2/1 in the non-limiting example, wherein any of the components maydeviate by up to ±50% from the stated proportions. The solution may thenbe mixed (e.g., for one hour) and then filtered (e.g., using a syringewith a 1 μm filter). The fluorophore may then be added to formformulation 120 from precursor 110, and the mixing may be continued foranother hour. Formulation 120 then be evaporated and heated (e.g., in anon-limiting example, using a rotovap under pressure of 60-100 mbar andtemperature of 40-60° C.) to achieve increased photo-stability as foundout by the inventors and explained below.

ESOR—Epoxy Silica Ormosil Solution

Specifically, compared to process 90 of Reisfeld 2006, the inventorshave found out that replacing TMOS 91A by TEOS 102 and using differentsilane precursors 104 provide ESOR 106 which enables association ofrhodamine-based fluorescent (RBF) compounds 115 in resulting films 130which are usable in displays 140, which prior art ESOR 92 does notenable. In particular, the inventors have used various silane precursors104 to enhance stability of, and provide emission spectrum tunability toRBF compounds 115 in produced film 130, as shown in detail below.

For example, silane precursors 104 may comprise any of MTMOS(methyltrimethoxysilane), PhTMOS, a TMOS with fluorine substituents,e.g., F₁TMOS (trimethoxy(3,3,3-trifluoropropyl)silane), F₀TEOS(Fluorotriethoxysilane) or F₂TMOS(tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane,1,2-bis(triethoxysilyl)ethane, trimethoxy(propyl)silane,octadecyltrimethoxysilane, fluorotriethoxysilane, andammonium(propyl)trimethoxysilane. The first three options areillustrated below.

In certain embodiments, Silane precursors 104 may comprise anyalkoxysilane, with R¹, R², R³ typically consisting of methyl or ethylgroups (e.g., R⁴—OSi(Me)₃), and R⁴ may consist of a branched orunbranched carbon chain, possibly with any number of halogensubstituents, as illustrated below.

In certain embodiments, silane precursors 104 may comprise any of:tetraalkoxysilane (e.g., tetraethoxysilane), alkyltrialkoxysilane,aryltrialkoxysilane, haloalkyltrialkoxysilane,heterocycloalkyltrialkoxysilane, N-heterocycletrialkoxysilane,(3-Glycidyloxypropyl)trialkoxysilane, haloalkyltrialkoxysilane,heterocycloalkyltrialkoxysilane, N-heterocycletrialkoxysilane, andcycloalkyltrialkoxysilane.

In certain embodiments, silane precursors 104 may be selected from anyof the following structures:

wherein T101 is an alkyl, T102 an aryl, T103 an haloalkyl, T104 anheterocycloalkyl (including a N-heterocycle) and T105 an cycloalkyl, asdefined herein.

In certain embodiments, ESOR may be prepared by first mixing the TEOSand the at least one silane precursor(s) under acidic conditions andthen adding the GLYMO. The acidic conditions may be adjusted by addingacetic acid, and be followed by adding water and alcohol(s) such asethanol, propanol, 2-propanol or butanol.

In certain embodiments, the volumetric ratio between TEOS:MTMOS or othersilane precursor(s):GLYMO may be between 1:1:1.5-2; and the volumetricratio between TEOS: silane precursor(s):acetic acid:alcohol:water may bebetween 1:1:0.01-1:1-10:4-8. ESOR mixing time may be reduced to fiveminutes. Any of the components may deviate by up to ±50% from the statedproportions.

In some embodiments (e.g., additional variants 107), ethanol and/orwater are not used, to simplify the process. For example,diphenylsilanediol (DPSD) may be used to provide a water-free matrix,avoiding the first hydrolysis step in the condensation.

In some embodiments (e.g., additional variants 107), citric acid and/orascorbic acid may replace or be added to the acetic acid.

DURS (Diurethane Siloxane)—Nanoparticles Powder

The inventors have found out that using ethylene glycol 108 for DURS 109instead of polyethylene glycol 94A for DURS 95 (as in Reisfeld 2006)enables better control of the film production and better films 130 thanprior art sol-gel precursors 96, as explained below.

The isocyanate-functionalized silica nanoparticles (Si NP) may comprise(isocyanato)alkylfunctionalized silica nanoparticles and/or3-(isocyanato)propyl-functionalized silica nanoparticles, which may beprepared from precursors (isocyanato)alkylfunctionalized trialkoxysilaneand/or 3-(isocyanato)propyltrietoxysilane, respectively.

The DURS may be prepared by mixing and refluxing the silicon andglycolated precursors. In some embodiments, the ethylene glycol may beadded in excess. In some embodiments, the reflux may be followed bycooling and filtration steps. In some embodiments, chlorobenzene(C₆H₅Cl) may be added to the mixture before the reflux step. In someembodiments, the chlorobenzene (C₆H₅Cl) may be evaporated prior to thecooling step. In an example, DURS was prepared by refluxing3-isocyanatopropyl functionalized nanoparticles and ethylene glycol. Inone embodiment, about 50-150 mg of 3-isocyanatopropyl functionalizedsilica nanoparticles (with 200-400 mesh, 1.2 mmol/g loading) and 16-320μl of ethylene glycol were refluxed in chlorobenzene for about 2-6hours. The functionalized silica nanoparticles were then separated fromthe chlorobenzene by a rotary evaporator.

In some embodiments (e.g., additional variants 107), DURS is not used,to simplify the process.

Transition Metal(s) Alkoxide Matrix Solution

Transition metalalkoxide matrix solution may comprise alkoxides of oneor more transition metals. For example, a zirconia (ZrO₂) matrixsolution may be prepared from zirconium tetraalkoxide, e.g., Zr(OPr)₄and/or zirconium, mixed with alcohol (e.g., propanol) under acidicconditions (e.g., in the presence of acetic acid, citric acid and/orascorbic acid). Various transition metals alkoxides may be used in placeor in addition to zirconia.

In certain embodiments, the ESOR may be mixed with the zirconia matrixsolution at a 2:1 volumetric ratio, and the DURS may then be added tothe mixture to provide, after mixing (e.g., for 1-5 hours) andfiltering, hybrid sol-gel precursor formulations. The zirconia matrixsolution may be configured to catalyze the epoxy polymerization of theESOR. In some embodiments, the zirconia matrix solution may be added tothe ESOR after e.g., 15, 30, 45 minutes. The subsequent mixing time maybe decreased down to 10 minutes.

In some embodiments, other metal oxide matrix may be used instead or inaddition to zirconia matrix during the sol-gel process, such as titaniausing titanium isopropoxide or boron oxide using boric acid. Zirconiaand/or alkoxides from transition metals such as boron alkoxide 103 maybe used in preparing sol-gel precursor 110.

Formulation

Formulations 120 comprise hybrid sol-gel precursor formulations 110 andat least one RBF compound 115 such as red-fluorescent RBF compound(s)and green-fluorescent RBF compound(s) which may be configured to emitthe R and G components of the required RGB illumination, provided by thedisplay's backlight unit (red-fluorescent RBF compounds emit radiationwith an emission peak in the red region while green-fluorescent RBFcompounds emit radiation with an emission peak in the green region). Itis emphasized that formulations 120 are very different from prior artlaser dye formulation 97 as laser dye usage as gain medium is verydifferent from the operation of fluorescent films in the backlight unit,e.g., concerning stability, emission spectra and additional performancerequirement as well as operation conditions.

Stages of methods 200—namely preparing hybrid sol-gel precursorformulation 110 (stage 210), mixing in RBF compound(s) 115 to formformulation 120 (stage 220), forming film 130 (stage 230) and optionallyevaporating alcohols prior to film formation (stage 225)—are shownschematically and explained in more detail below.

The mixture of the hybrid sol-gel precursor formulation and the RBFcompound(s) may be stirred and then evaporated and heated (e.g., in anon-limiting example, stirred for between 20 minutes and three hours,evaporated at 60-100 mbar and heated to 40-60° C.) to increase thephoto-stability of the RBF compound(s) (see additional process detailsbelow). Process parameters may be adjusted to avoid damage to thefluorescent dyes, control parameters of the sol gel process and optimizethe productivity in the process.

The concentration of the RBF compound(s) may be adjusted to determinethe final peak emission intensity excited by the chosen backlight unitand may range e.g., between 0.005-0.5 mg/ml. It is noted that multiplefluorescent molecules having different emission peaks may be used in asingle formulation 120. The processes may be optimized to achieverequired relations between the RBF compound(s) and the other componentsof the film, e.g., to achieve any of supramolecular encapsulation of theRBF compound(s) in the sol gel matrix, covalent embedding of the RBFcompound(s) in the sol gel matrix (e.g., via siloxane bonds), and/orincorporation of the RBF compound(s) in the sol gel matrix.

Silane precursors 104 may be selected according to the used RBFcompound. For example, the inventors have found out that PhTMOS may beused to stabilize red-fluorescent RBF compounds. In another example, theinventors have found out that TMOS with fluorine substituents may beused to stabilize red-fluorescent RBF compounds. Modifying and adjustingparameters of the substituents was found to enable control of thephotostability and emission characteristics of the fluorescentcompounds. In yet another example, the inventors have found out thatF₁TMOS may be used to stabilize green-fluorescent RBF compounds. Theseand more findings are presented below in detail.

Optimizing the Silane Precursors in the ESOR to Stabilize and Tune theFluorescent Molecules

Films 130 prepared from formulation 120 may comprise ESOR 106 preparedfrom TEOS 102, at least one silane precursor 104 (and/or MTMOS 91B), andGLYMO 91C; DURS powder 109 prepared from isocyanate-functionalizedsilica nanoparticles 94B and ethylene glycol 108; a transition metal(s)alkoxide matrix solution 103; and at least one RBF compound 115,selected to emit green and/or red light and being supramolecularlyencapsulated and/or covalently embedded within film 130. Silaneprecursors 104 may comprise any of MTMOS, PhTMOS, a TMOS with fluorinesubstituents, F₁TMOS, F₂TMOS(tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane,1,2-bis(triethoxysilyl)ethane, trimethoxy(propyl)silane,octadecyltrimethoxysilane, fluorotriethoxysilane, andammonium(propyl)trimethoxysilane. For example, for film 130 and/or filmlayer 134 with red-fluorescent RBF compound, silane precursor 104 maycomprise PhTMOS and/or a TMOS with fluorine substituents. In anotherexample, for film 130 and/or film layer 132 with green-fluorescent RBFcompound, silane precursor 104 may comprise F₁TMOS.

Examples are provided below for four matrix compositions (Z₁, Z₂, Z₃,Z₄) for mixtures of ESOR and zirconia matrix solution having thecomponents Zr(PrO)₄: GLYMO:TEOS:silane precursor atn=0.011:0.022:0.013:0.021 (moles), with the silane precursor being MTMOSin Z₁, PhTMOS in Z₂, F₁TMOS in Z₃, and F₂TMOS in Z₄, as illustratedbelow.

These matrices were mixed with several dyes and tested, as correspondingfilms 130, for quantum yield and lifetime, as presented in detail below,with results presented in Table 1. All but the rows marked by theasterisk employ evaporation of alcohols prior to film formation (stage225). The lifetime was defined as a reduction to 80% of the initialemission intensity (measured by a fluorimeter) or up to 3 nm change inwavelength peak position, was measured in accelerated procedures and isshown as a relative value (factor) relative to the reference sample Z₁(MTMOS) in the first line. RBF compounds ES-61 and RS-130 arered-fluorescent, RBF compound JK-71 is green-fluorescent, and theirstructures are provided above. The emission peak wavelengths in lines1-4 and 9 vary according to the concentration of the fluorophore and thethickness of the sol-gel layer. The data was measured with a blue lightflux of 100 mW/cm² and temperature of 60° C. for the green RBF compoundsand with a white light flux of 20 mW/cm² and temperature of 60° C. forthe red RBF compounds.

TABLE 1 Optimization of the silane precursors Emission Fluorescent peakLifetime Matrix (silane compound (see wavelength Quantum multiplier #precursor) above) (nm) yield (factor) FWHM (full width at half maximum,nm) 1 Z₁ (MTMOS)* Green (JK-71) 35-40 535-550 55-75 Reference 2 Z₃(F₁TMOS) Green (JK-71) 525-540 80-90 ×3 3 Z₁ (MTMOS)* Red (ES-61) 40-45625-635 70-75 ×3 4 Z₂ (PhTMOS) Red (ES-61) 625-635 70-75 ×8 5 Z₃(F₁TMOS) Green (JK-71) 42 535 6 1:3 Z₂:Z₃ Green (JK-71) 538 7 1:1 Z₂:Z₃Green (JK-71) 540 8 Z₂ (PhTMOS) Green (JK-71) 543 9 Z₃ with JK-71 + Z₂with ES-61 Green 30-35 535-543 denoted EC-154 Red 45-50 633-642Approximate concentration Film in the film thickness (mg/mL) (μm) 10 Z₁(MTMOS)* Red (RS-130) 0.06 10 70% ×3 11 Z₁ (MTMOS) Red (RS-130) 0.06 1073% ×8 12 Z₂ (PhTMOS) Red (RS-130) 0.03 10 72% ×9 13 Z₂ (PhTMOS) Red(ES-61) 0.06 10 72% ×16  14 Z₂ (PhTMOS) Green (JK-71) 0.075 538 85% same15 Z₃ (F₁TMOS) Green (JK-71) 0.15 80 535 88% ×3 16 Z₄ (F₂TMOS) Green(JK-71) 0.15 522 80% same 17 Z₂ (PhTMOS) Red (RS-130) 0.03 623 72% ×9 18Z₃ (F₁TMOS) Red (RS-130) 0.06 618 67% ×4 19 Z₄ (F₂TMOS) Red (RS-130)0.06 616 73% ×10  *No evaporation of alcohols prior to film formation

Table 1 demonstrates the capabilities of the disclosed technology toincrease the lifetime of RBF compound(s) in film 130 multiple times over(eight fold—line 4 vs. line 1, fivefold—line 13 vs. line 10), reach highquantum yields (above 80%—lines 2, 14 15), tune the emission peakwavelength of the RBF compound(s) significantly (lines 5-8, 14-16,17-19) and provide tuned multi-layered films 130 (line 9). Specifically,intercalating the red fluorescent compound(s) in the Z₂ matrix resultedin increased photo-stability, intercalating the green fluorescentcompound(s) in the Z₃ matrix resulted in increased photo-stability andimproved the QY (quantum yield) compare to the Z₁ matrix. When combiningthe precursor of Z₂ and Z₃ together, changing the PhTMOS:F₁TMOS ratiocan provide tuning of the green wavelength (lines 5-8).

The inventors have also found out that the length of the carbon chain ofthe silane precursor(s) may contribute to the stability of thered-fluorescent RBF compounds; in certain embodiments the carbon chainmay consist of 8, 9, 10, 12 or more carbon atoms, possibly withcorresponding fluorine atom as hydrogen substituents. In certainembodiments, some or all fluorine atoms may be replaced by anotherhalogen such as chlorine. Moreover, the inventors have found out thatmodifying the length and hydrophobic\hydrophilic degree of the chain maybe used to further tune and adjust the emission peak (beyond the dataexemplified above), according to requirements.

FIGS. 7A and 7B are examples for illustrations of characteristics offormulations and films according to some embodiments of the invention.FIG. 7A exemplifies the tuning of the emission spectrum (tuning of theemission peak is indicated by Δλ) by adjusting formulation 120, theillustrated cases corresponding to line 15 (JK-71 in Z3 with peak at 535nm) and line 8 (JK-71 in Z2 with peak at 543 nm) in Table 1. FIG. 7Bexemplifies the implementation of formulation 120 with two fluorescentcompounds and different respective precursors indicated in line 9 inTable 1 (Z₃ with JK-71+Z₂ with ES-61) providing two different emissionpeaks.

In certain embodiments, silane precursors 104 may comprise, in additionor in place of silane precursor 104 disclosed above, at least one of:1,2-bis(triethoxysilyl)ethane, trimethoxy(propyl)silane,octadecyltrimethoxysilane, fluorotriethoxysilane,ammonium(propyl)trimethoxysilane (illustrated below) and any furthervarieties of any of disclosed silane precursor 104.

Film Preparation

Films 130 may be prepared from formulations 120 using a transparentsubstrate (e.g., glass, polyethylene terephthalate (PET), polycarbonate,poly-methyl-methacrylate (PMMA) etc.) or as stand-alone films (aftersolidification), and be used as color-conversion films in backlightunits of displays. The substrate may be scrubbed to increase the surfaceroughness or be laminated to provide diffuser properties—in order toincrease scattering or diffusing of blue light from the backlight unit.

Spreading formulation 120 may be carried out by any of manual coating(blade or spiral bar), automatic coating (blade or spiral bar), spincoating, deep coating, spray coating or molding; and the coatings may beapplied on either side or both sides of the transparent substrate.Multiple layers of formulation 120 may be applied consecutively to film130 (film thickness may range between 10-100 μm).

Concerning the drying, or curing process of formulation 120, it may be atwo-step process comprising an initial short term curing at a highreaction rate for determining the formation of the sol-gel matrix and along term curing at a lower reaction rate for determining the completionof the reaction (the temperature and duration of this step may be set todetermine and adjust the reaction results). The initial short termcuring (drying) maybe carried out by a hot plate, an oven, a drierand/or an IR (infrared) lamp. In a non-limiting example, film 130 onglass may be placed on top of a hot plate or in an oven and undergo theheating profile: constant temperature (e.g., 60-100° C. for 1-3 hours)followed by step-wise temperature increments (e.g., 3-5 steps of 20-40°C. increase during 15-90 minutes each). In another non-limiting example,filmed may be cured by a drier or an IR lamp, e.g., being set on aconveyor (moving e.g., in 0.1-5 m/min) and heated to temperaturesbetween 60-100° C. The curing may be configured to avoid film annealingand provide a required mesh size, while maintaining and promoting thestability of the RBF compound(s) 115. Curing parameters may be optimizedwith respect to a tradeoff between photostability and brightness, whichrelate to the film density resulting from the curing. In case of filmswith multiple layers (e.g., up to twenty layers), additional curing maybe carried out between layer depositions (e.g., 50-90° C. for 1-3 hours)and a final curing may be applied after deposition of the last layer(e.g., 100-200° C. for 2-72 hours). In some embodiments, lower curingtemperatures may be applied for longer times, e.g., the curing may becarried out for a week in 50° C. In some embodiments, curingtemperatures may be raised stepwise, possibly with variable durations,e.g., the curing may be carried out stepwise at 30° C., 60° C., 90° C.,two hours at each step. Optionally a final curing stage (e.g., at 130°C.) may be applied.

For example, green-fluorescent RBF compound in Z₃ (F₁TMOS) matrix wascured under different heat transport regimes: IR only (IR intensity 10%;25 min on the conveyor moving at 0.1 m/min) dryer only (at consecutive15 min steps of 30° C., 50° C., 70° C., 90° C., 110° C.) and acombination of IR followed by dryer, with a final curing of 24 h in anoven at 130° C. The samples maintained their emission peaks, FWHM (fullwidth at half maximum) and QY, and exhibited the following reduction ofemission intensity after eight days with respect to the initialintensity (measured by a fluorimeter): IR only—54%, dryer only—79%, IRand dryer—73%, showing the efficiency of the latter two methods.

The process may be further adjusted to yield encapsulation or bonding ofthe RBF compound(s) 115 in the matrix which narrows the FWHM of theemission band by adjusting the micro-environment of the fluorescentmolecules. The process may be monitored and optimized using any ofquantum yield measurements, fluorescent measurements, photometricmeasurements, photostability (lifetime) testing and others.

Concerning display properties, it is noted that emission peaks may berelated to the display hue property and the FWHM may be related to thedisplay saturation property. The adjustment of the hue and saturationproperties may be carried out by corresponding adjustments in one ormore components of formulation 120 and/or in the film production processdescribed above. It is further noted that additional display propertiessuch as intensity/lightness and brightness/LED power may be adjustedwith respect to the designed film properties.

Preparation and Measurement Details—Examples

The following illustrates some experimental procedures used to derivethe results presented above (see FIG. 6A for overview). These proceduresare not limiting the application of the disclosed invention.

In a first example, film 130 was prepared by applying ten layers offormulation 120 with green-fluorescent RBF compound at a concentrationof 0.1 mg/ml in the formulation, layer by layer, onto a transparentsubstrate and then applying two layers of formulation 120 withred-fluorescent RBF compound at a concentration of 0.05 mg/ml in theformulation, layer by layer, onto the former, green emitting layers. Theinventors later found out that the multiple green-fluorescent layers maybe replaced by fewer or even a single layer when evaporation of thealcohols is carried out prior to the layer application. FIG. 8Aillustrates the resulting spectrum, having a first emission peak at617±3 nm (red) and a FWHM of around 50 nm; and a second emission peak at540±3 nm (green) and a FWHM of around 45 nm, according to someembodiments of the invention. The quantum yield of the film was measuredby a fluorimeter having an integrating sphere to be around 70-90%depending on the RBF compound and the lifetime at the device level wasestimated to be in the range of 20,000 to 50,000 hours. FIG. 8Billustrates the CIE 1931 color gamut diagram for the film, compared toNTSC and sRGB standards, according to some embodiments of the invention.As seen in the diagram, the color gamut range of film 130 in display 140is larger than the standard LCD (sRGB) gamut and is in the range of theNTSC standard gamut.

In a second example, thirteen layers of green-fluorescent formulationwere applied instead of ten layers as in the first example. FIG. 8Cillustrates the resulting emission spectrum, according to someembodiments of the invention. The resulting change of spectrum isillustrated by comparing FIG. 8A for the film prepared in the firstexample with FIG. 8C for the film prepared in the second example. Therelative intensity of the peak at around 550 nm attributed to the greenlight is higher in FIG. 8C in comparison to the relative intensity ofthe corresponding peak in FIG. 8A and thus demonstrates that the whitepoint position may be tuned as desired by changing the structure of film130, e.g., by adjusting the number of layers and/or concentration informulation 120 of either RBF compound.

In a third example, consecutive layers of sol-gel formulation 120 wereapplied directly on light source 80 (in the non-limiting example, onblue light source 80A which emits at a wavelength range of about 400-480nm) or in close proximity thereto. In the example, bothgreen-fluorescent and red-fluorescent RBF compounds were mixed informulation 120 and applied as film 130 comprising ten layers to blueLED light source 80A. Correspondingly, FIG. 8D illustrates the resultingemission spectrum, having a first emission peak at 621 nm (red) and asecond emission peak at 512 nm (green), both peaks exhibiting a FWHM inthe range of 40-50 nm (the peak at 450 nm corresponds to the lightsource blue emission), according to some embodiments of the invention.

In a third example, some embodiments of used red-fluorescent RBFcompounds 115 were 5- and 6-Carboxy X-rhodamine—Silylated illustratedbelow. The illustrated derivative of RS-130 red RBF compound is anon-limiting example, similar covalent binding of RBF compounds 115 tothe sol gel matrix may be achieved with other RBF compounds in similarways.

In the example, precursor 110 was configured to covalently bind the RBFcompounds to the sol-gel matrix. ESOR 106 was prepared by stirredover-night 3 mg of a mixture of the RBF compounds, 10 ml of ethanol and3.6 ml of H₂O to yield the ESOR. On the next day 3 ml of TEOS and 3 mlof MTMOS and 2500 of acetic acid were added to the ESOR mixture, whichwas then stirred for 10-15 minutes. Finally, 4.8 ml of GLYMO were addedto the mixture and stirred for two hours. Zirconia 93 (as a non-limitingexample for transition metal(s) alkoxide matrix solution 103) wasprepared by stirring together 10 ml of zirconium n-tetrapropoxide inpropanol and 3 ml of acetic acid for 10 minutes. 3.3 ml of acetic acidin H₂O (1:1 ratio) and 20 ml of isopropanol were added to the mixtureand stirred for another 10 minutes. DURS 109 was prepared by refluxingof 90 mg of 3-isocyanato propyl functionalized silica nanoparticles and32 μl of ethylene-glycol in chlorobenzene for two hours. The ethyleneglycol functionalized nanoparticles were separated from thechlorobenzene by an evaporator. Precursor 110 was prepared by mixing theDURS nanoparticles with 8 ml of the ESOR and 4 ml of ZrO₂ solution. Thefinal concentration of the (red-fluorescent) RBF compounds informulation 120 was 0.08 mg/ml. The mixture is stirred for over one hourand then filtrated. Film 130 was prepared from formulation 120 and itsmeasured emission peak was 610±5 nm with FWHM of 50±5 nm, with theemission curve illustrated in FIG. 8E.

In a forth example, some embodiment of used red-fluorescent RBFcompounds 115 were 5- and 6-Carboxy X-rhodamine-Silylated, illustratedabove. In the example, precursor 110 was configured to covalently bindthe RBF compounds to the sol-gel matrix. ESOR 106 was prepared undereither acidic or basic conditions, the former proving to be a betteralternative. Under acidic conditions, 4.9 mg of a mixture of the RBFcompounds, 10 ml of ethanol, 3.6 ml of H₂O and 125 μl of acetic acidwere stirred over-night to yield the ESOR. Alternatively, under basicconditions, 9.6 mg of the RBF compounds, 10 ml of ethanol, 3.41 ml ofH₂O and 242 μl of ammonium hydroxide 28% were stirred over-night toyield the ESOR, and on the next day, 125 μl of acetic acid were added tocounteract the ammonium hydroxide. In either case, on the next day 3 mlof TEOS and 3 ml of MTMOS and 125 μl of acetic acid were added to theESOR mixture, which was then stirred for 10-15 minutes. Finally, 4.8 mlof GLYMO were added to the mixture and stirred for two hours. Zirconia93 (as a non-limiting example for transition metal(s) alkoxide matrixsolution 103) was prepared by stirring together 10 ml of zirconiumn-tetrapropoxide in propanol and 3 ml of acetic acid for 10 minutes. 3.3ml of acetic acid in H₂O (1:1 ratio) and 20 ml of isopropanol were addedto the mixture and stirred for another 10 minutes. DURS 109 was preparedby refluxing of 90 mg of 3-isocyanato propyl functionalized silicananoparticles and 32 μl of ethylene-glycol in chlorobenzene for twohours. The ethylene glycol functionalized nanoparticles were separatedfrom the chlorobenzene by an evaporator. Precursor 110 was prepared bymixing the DURS nanoparticles with 8 ml of the ESOR and 4 ml of ZrO₂solution. The final concentration of the RBF compounds in formulation120 was 0.13 mg/ml when prepared under acidic conditions and 0.46 mg/mlwhen prepared under basic conditions. The mixture was stirred for overone hour and then filtrated.

Cross-Linking with PMMA

Some embodiments comprise fluorescent compounds which are bonded to PMMAand have Si linkers to bond the PMMA-bonded compounds to the sol-gelmatrix.

The following non-limiting examples illustrate binding RBF compounds toPMMA by showing the preparation of RBF compound ES-87 and cross-linkingit with PMMA and linker of Si to be bonded to the sol-gel matrix. ES-86was prepared as a precursor by dissolving 3-bromopropanol (0.65 ml, 7.19mmol, 1 eq) in dry DCM (dichloromethane) under N₂ atmosphere. NEt₃ (0.58ml, 7.91 mmol, 1.1 eq) was added and the mixture was cooled to 0° C.Acryloyl chloride (1.1 ml, 7.19 mmol, 1 eq) was added dropwise and themixture was heated to room temperature and stirred at this temperaturefor 2 h. Upon completion, the mixture was quenched with 0.4 ml MeOH,diluted with DCM and was washed with saturated NaHCO₃. The organic layerwas separated, dried with Na₂SO₄, filtered and the solvent was removedunder reduced pressure. The crude product was purified by columnchromatography (SiO₂, 10% EtOAc/Hex) to give the product as a colorlessoil (943 mg, 68% yield).

ES-87 was then prepared by dissolving RS-106 (see below, 150 mg, 0.26mmol, 1 eq) in 3 ml dry DMF (dimethylformamide) under N₂ atmosphere.K₂CO₃ (55 mg, 0.4 mmol, 1.5 eq) was added and the mixture was stirredfor 5 min before ES-86 (154 mg, 0.8 mmol, 3 eq) was added. The mixturewas stirred for 3 hours at room temperature. Upon completion, themixture was diluted with DCM and was washed with brine. The organiclayer was separated, dried with Na₂SO₄, filtered and the solvents wereremoved under reduced pressure. The crude product was purified by columnchromatography (SiO₂, DCM to 10% MeOH/DCM) to give the product as a bluepowder (147 mg, 75% yield).

ES-87 was used to prepare cross-linked dyes as explained below in threenon-limiting examples.

ES-91 was prepared by charging a 50 ml round-bottom flask with dry EtOH(9 ml) and N₂ was bubbled through for 20 min. Methyl methacrylate (0.3ml, 2.8 mmol, 1 eq), ES-87 (4 mg, 0.0056 mmol, 0.002 eq) and AIBN(azobisisobutyronitrile, 10 mg, 0.056 mmol, 0.02 eq) were added and N₂was bubbled through for 10 min. The reaction mixture was heated toreflux under N₂ atmosphere for 24 h. Upon completion, the mixture wascooled to room temperature and was evaporated to dryness under reducedpressure. The crude product was dissolved in 3 ml of DCM and then wasadded dropwise to 50 ml of Hex. The precipitate was filtered and thepurification process was repeated again to give the product as a bluepowder.

ES-99 was prepared by charging a 50 ml round-bottomed flask with dryEtOH (9 ml) and N₂ was bubbled through for 20 min. Methyl methacrylate(0.3 ml, 2.8 mmol, 1 eq), 3-methacryloxypropyl trimethoxysilane (34 μl,0.14 mmol, 0.05 eq), ES-87 (8 mg, 0.01 mmol, 0.002 eq) and AIBN (10 mg,0.056 mmol, 0.02 eq) were added and N₂ was bubbled through for 10 min.The reaction mixture was heated to reflux under N₂ atmosphere for 24 h.Upon completion, the mixture was cooled to room temperature and wasevaporated to dryness under reduced pressure. The crude product wasdissolved in 3 ml of DCM and then was added dropwise to 50 ml of Hex.The precipitate was filtered and the purification process was repeatedagain to give the product as a blue powder.

ES-113 and ES-110 were prepared similarly to ES-99, but using higherconcentration of the linker 3-methacryloxypropyl trimethoxysilane,namely 50% and 100% linker respectively, compared with 5% in ES-99. FIG.9 schematically illustrates some embodiments of PMMA cross-linked dyes,according to some embodiments of the invention.

Protective Films

Some embodiments comprise applying a protective film 131 to colorconversion film 130 and/or configuring color conversion film 130 to haveprotective properties which prevent humidity damages and cracking. Anytype of color conversion film 130 may be protected and/or enhanced asdescribed in the following, e.g., RBF-compounds-based films 130 as wellas films 130 based on other organic or inorganic fluorescent moleculesand quantum-dot-based color conversion films 130.

For example, protective film 131 may be formed using zirconium-phenylsiloxane hybrid material (ZPH), a transparent, clear and flexiblepolymer, based on the description in Kim et al. 2014 (“Sol-gel derivedtransparent zirconium-phenyl siloxane hybrid for robust high refractiveindex led encapsulant”, ACS Appl. Mater. Interfaces 2014, 6, 3115-3121),with the following modifications, found by the inventors to isolatefilms 130 from the surroundings, provide the film mechanical support andprevent cracks.

ZPH is a silica based polymer gel, cured in hydrosilylation additionreaction. The polymer comprises two resin components: HZPO (a Si—Hfunctionalized silica) and VZPO (a vinyl functionalized silica). Bothcomponents are synthesized in a sol-gel reaction separately and thenmixed in the proper ratio into formulation 120 and cured to yield asemi-solid form. HZPO was mixed from 3.2 ml Methyldiethoxysilane (MDES),6.5 g diphenylsilanediol (DPSD) and 25 mg amberlite IRC76 for 1 hour at100° C. and then, while stirring, 673 μL zirconium propoxide (ZP) 70% in1-propanol was added slowly and the reaction continued overnight. VZPOwas mixed from 3.1 g vinyltrimethylsilane (VTMS), 4.4 g DPSD and 7.7 mgbarium hydroxide monohydrate in 0.86 ml p-xylene at 80° C. and then,while stirring, ZP was added slowly, with the reaction time being fourhours. ZPH was prepared by mixing VZPO and HZPO in a ratio of 1:1mol/mol and 10 ml of a platinum catalyst was added to the viscousliquid, which was then stirred vigorously for one minute and applied onthe substrate using a coating rod. Protective film 131 was inserted intothe oven in 150° C. for three hours for curing.

Additional examples for protective films 131 include using polymerizedMMA (methyl-methacrylate) as protection, by allowing MMA to diffuse intothe sol-gel pores. Color conversion films 130 may be coated withadditional MMA monomers that penetrate the sol-gel pores and thenpolymerize inside, thereby improving the life time of film 130. Thepreparation procedure may be modified to provide such polymerizationconditions.

Some embodiments comprise using a trimethoxysilane derivative ascoating, e.g., an R-TMOS coating with R being e.g., phenyl, methyl,CH₂CH₂CF₃ or other groups, with proper process adaptations which providethe coating conditions for forming protective film 131 and/or protectivecharacteristics of film 130.

Some embodiments comprise using as ESOR layer as protective coating 131,such as ESOR with no dye as protective layer 131 applied on cured film130. Other protective coatings 131 of film 130 may comprise an aceticanhydride surface treatment derived from acetic acid with ending —OHgroups changed to —Ac groups to enhance life time and/orchlorotrimethoxysilane protective layer 131 having endings with —OHgroups modified to -trimethylsilane to enhance life time.

In certain embodiments, disclosed protective films 131 may be used in arange of applications for protective respective films from humidity andmechanical damages. For example, disclosed protective films 131 may beused to coat various plastic films (made of e.g., PEI(polyethylenimine), acrylic polymers, polycarbonate, PET, PDMS(polydimethylsiloxane) and related siloxanes, as well as otherpolymers), glass and metals/metal oxide films or surfaces (e.g., ofcopper, silicon, silicon oxides, aluminum, titanium and other transitionmetals and their oxides). Protective films 131 may be configured to havecorresponding good adhesion to the respective films.

In some embodiments, protective films 131 may be used to coat diffusers,polarizers, glasses or any other film that needs temperature andhumidity protection (e.g., up to 85° C., 95% relative humidity).

In some embodiments, protective films 131 and/or formulations thereofmay be used as fillers in porous films.

UV Curing Processes

UV curing processes may be used additionally or in place of sol gelprocesses to provide the color conversion films. Formulations withoutand with rhodamine-based fluorescent compounds, films, displays andmethods are provided, in which the fluorescent compounds are stabilizedand tuned to modify display backlight illumination in a manner thatincreases the display's efficiency and widens its color gamut. UV curedformulations may be used to provide fluorescent films that may beapplied in various ways in the backlight unit and/or in the LCD paneland improve the display's performance. The formulation, curing processand film forming procedures may be optimized and adjusted to provide ahigh photo stability of the fluorescent compounds and narrow emissionpeaks of the backlight unit.

In certain embodiments, the sol gel process may be replaced by a UVcuring process, with respect to some or all layers of film 130. Similaror different RBF compounds 115 may be used in UV cured layers, such asRBF compounds disclosed above, and films 130 produced by UV curing mayreplace (or complement) films 130 (or layers 132 and/or 134) produced bythe sol gel processes in the configurations of backlight unit 142 anddisplay 140 which are illustrated in FIGS. 4A-4E and the relateddisclosure. Other organic or inorganic fluorescent dyes as well asquantum dots may be embedded in disclosed UV cured films 130 ormodifications thereof as well. Also, configurations of film 130disclosed above in relation to display configurations, polarizing filmsand red enhanced films may be implemented with UV cured films 130 orlayers 132, 134. In the following, examples for applicable UV processesare presented.

In some embodiments, UV curing is advantageous due to the wide range ofUV curable materials, which provide an opportunity to create polymericmatrices which are compatible with the incorporated dyes, such as RBFcompounds 115. In order to achieve maximal life time and QY, thestructure and the crosslinking density may be optimized and theinteraction between the dye and the matrix may be minimized. The usedone in UV curing of highly reactive components may significantly reducethe amount of non-crosslinked material even at low UV exposure and shortretention time—thereby enabling to minimize damage to the dye moleculeswhile providing required matrices for the dye, e.g., matrices whichprovide high photostability, narrow FWHM (e.g., 40-60 nm) and high QY inthe green and red regions (e.g., due to less occupied vibration levels),for RBF compounds 115 or other fluorescent molecules). The cross-linkingdegree may be optimized per dye material in order to obtain high QY (toomuch cross linking may degrade the QY).

Various examples are presented below for formulations 120 which are thenUV cured after being applied to transparent PET (polyethyleneterephthalate) substrate or diffuser films (PET coated with PMMAcoating) by drawing using coating rods for providing films with widthsranging 20-100μ which are then irradiated once under “H” UV lamp atconveyor speed 2-7 m/min. Color conversion films 130 may comprisemultiple layers which may be applied one on top of the iother. Resultingcolor conversion films 130 (or protective films 131, see below) may beused as explained above by themselves or in combination with films 130produced by sol gel processes 200. Formulations 120 for UV cured films130 may comprise RBF compounds 115 as described above. Life times offluorescent dyes in UV cured matrix are different for different dyes anddepend on the cured formulation and on the curing conditions. Generally,the stability of RBF compounds 115 under continued blue light excitationprovides a long life time.

UV cured films 130, in particular UV cured color conversion films 130,may be prepared from formulations 120 comprising 65-70% monomers, 25-30%oligomers, and 1-5% photointiator; as well as color conversion elementssuch as RBF compounds at low concentration (e.g., 0.005-0.05%).Following are non-limiting examples for such formulations 120, which areUV cured to yield respective films 130, in weight percentages of thetotal formulation.

Some examples comprise formulations 120 being a mixture of theingredients listed in Table 2, such as the five specific formulationspresented as non-limiting examples. The liquid photoinitiator blendused, in a non-limiting manner, was GENOCURE* LTM liquid photoinitiatorblend for UV-curable inks, coatings and adhesives, which has goodabsorption between 350 and 400 nm.

TABLE 2 UV cured formulations. Formulation number and w/w % in theformulation Ingredient 1 2 3 4 5 Monomers DPGDA (dipropylene glycoldiacrylate) 17.4 Ditrimethylolpropane tetraacrylate 28.3 27.6 28.3Dipentaerythritol hexaacrylate 22.2 22.2 24.7 24.1 22.2 Ethoxylatedpentaerythritol 27.8 tetraacrylate Propoxylated (3) glyceryl acrylate16.1 15.6 15.7 16.2 TMPTA (Trimethylolpropane 27.5 triacrylate)Oligomers Polyester acrylate 27.4 Modified polyester resin diluted 27.9with dipropyleneglycol diacrylate Aliphatic urethane hexaacrylate 28.426.9 28.3 Photoinitiators Alpha-hydroxy-cyclohexyl- 4.9 phenyl-ketoneDifunctional alpha-hydroxy 4.9 5.1 5.1 ketone Liquid photoinitiatorblend 5.1 Dyes RBF compounds JK-32 or RS56 0.036 0.042 0.017 Dyerhodamine 110 0.016 Dye rhodamine 101 inner salt 0.029 RBF compoundES-61 0.008

Formulations 1 and 2 were prepared by mixing all the ingredients, exceptthe respective dyes, at a temperature of 50° C. and cooling the mixtureto room temperature. Mixing of formulation 3 was performed withoutheating. Then the respective dye was added and sonication was used todissolve the dye into formulation 120. Formulation 4 was prepared bymixing and sonication of a first part with rhodamine 110 and a secondpart with JK-32. Each part was prepared like formulations 1 and 2. Thesamples were applied to transparent PET substrate by drawing using acoating rod to 100 μm and irradiated once under H UV lamp at conveyorspeed 2-5 m/min. Formulation 5 was prepared by mixing all theingredients, except ES-61, at temperature 50° C. and cooling the mixtureto room temperature. Then ES-61 was added and the mixture was sonicateduntil the dye was dissolved. The sample was applied to the back side ofdiffuser 144 (of backlight unit 142) by drawing using a 80 μm coatingrod (indicating a nominal thickness number, the actual coating thicknessdepends on the chemical properties of the coating compounds such asviscosity), and irradiated once under H UV lamp at conveyor speed of 7m/min. QY measurements were carried out using an integrating spherecoupled to a fluorimeter (the error margin was about 5%). Resulting QY'swere 52% at 616 nm, 55% at 609 nm, 51% at 616 nm, 53% at 529 and 611 nm,and 71% at 624 nm for formulations 1-5, respectively. The FWHM of allformulations ranged between 40-60 nm. FIG. 10 illustrates the emissionspectra of formulations 1-4, respectively, according to some embodimentsof the invention.

The produced films may be combined and optimized to form film 130, forexample a non-limiting example of film 130 was optimized to operate witha blue backlight source 80A of about 10 mW/cm² of optical power andprovided a red emission peak at 616 nm with FWHM of 60 nm and a greenemission peak at 535 nm with FWHM of 45 nm, with a white point at (0.30,0.27) CIE 1931 coordinates (white point adjustment may also be carriedout as disclosed above). FIG. 11 illustrates the emission spectrum offilm 130 and its color gamut with respect to sRGB, NTSC and aquantum-dots-based display, according to some embodiments of theinvention. The color gamut provided by film 130 is similar to the colorgamut defined by NTSC.

Formulations 1-5 are shown with red fluorescent RBF compounds and may beused as red-enhancing films 130 in displays with white light source80B—as illustrated in FIGS. 5A and 5B which were discuss in detailabove.

FIG. 12A illustrates examples for absorption and emission spectra ofdisplays 140 with red-fluorescent RBF compound(s) films 130, accordingto some embodiments of the invention. Film(s) 130 may be used e.g., tored-enhance white LED displays as disclosed above under the sectiontitles “Red enhancement” and FIGS. 5A and 5B. The absorption spectrum offilm(s) 130 with red-fluorescent RBF compound(s) 115 has significantabsorption in yellow region 80B-Y (550-600 nm) and the fluorescentspectrum of film(s) 130 with red-fluorescent RBF compound(s) 115, usingYAG-based LEDs 80B (YAG—yttrium aluminum garnet, Y₃Al₅O₁₂) and measuredafter an LCD color display, shows the distinct peaks at the transmissionregions of the RGB filters.

FIG. 12B illustrates an example for a color gamut diagram of displays140 with red-fluorescent RBF compound(s) films 130, according to someembodiments of the invention. Compared to prior art gamuts such asindicated by sRGB (LCD) and NTSC (“National Television SystemCommittee”) standards, the gamut of disclosed display 140 is wider andextends into regions which are not represented by prior art displays,thereby providing better color representation. In particular is thegamut range of disclosed display 140 larger than sRGB in the green andin the red regions. Moreover, as disclosed herein, the tunability of thespectral range of RBF compound(s) 115 in films 130 by controlling thesol gel process (e.g., by adjusting silane precursors 104) may be usedto extend the color gamut even further, to the wavelength region beyond540 nm to 530 nm or over 520 nm, providing even wider gamuts.

In some embodiments, green fluorescent RBF compounds may be added tothese formulations or may be applied in separate formulations to formfilms added to red fluorescent films.

Some additional examples comprise formulations 120 being a mixture ofthe ingredients listed in Table 3, such as the five specificformulations presented as non-limiting examples.

TABLE 3 UV cured formulations. Formulation number and w/w % in theformulation Ingredient 6 7 8 9 10 11 Monomers DPGDA 17.0Ditrimethylolpropane 28.3 28.3 28.3 28.3 tetraacrylate Dipentaerythritolhexaacrylate 22.2 22.2 22.0 22.2 22.2 22.2 Ethoxylated pentaerythritol28.3 tetraacrylate Propoxylated (3) glyceryl 16.2 16.2 16.2 16.2 16.2acrylate TMPTA 28.0 Oligomers Polyester acrylate 28.3 28.3 Modifiedpolyester resin 28.0 diluted with dipropyleneglycol diacrylate Aliphaticurethane 28.3 28.3 28.3 hexaacrylate PhotoinitiatorsAlpha-hydroxy-cyclohexyl- 5.0 5.0 phenyl-ketone Difunctionalalpha-hydroxy 5.0 5.0 5.0 ketone Liquid type 1 photoinitiator 5.0 blendDyes RBF compound JK-32 0.03 0.03 0.03 RBF compound RS56 0.04 RBFcompound JK-71 0.03 RBF compound RS-106 0.02

Formulation 6 was prepared by mixing all the ingredients, except JK32,at a temperature of 50° C. and cooling the mixture to room temperature.Then JK32 was added and sonication was used to dissolve it. The sampleswere applied to the back side of diffuser 144 at a layer 60μ thick usinga coating rod and irradiated once under H UV lamp at conveyor speed 2m/min. Formulation 7 was prepared by mixing all the ingredients, exceptRS56, at a temperature of 50° C. and cooling the mixture to roomtemperature. Then RS56 was added and sonication was used to dissolve it.The samples were applied to a transparent PET substrate at a layer 60μthick using a 80 μm coating rod and irradiated once under H UV lamp atconveyor speed 2 m/min. Formulations 8 and 9 were prepared by mixing allthe ingredients, except JK32, at a temperature of 50° C. and cooling themixture to room temperature. Then JK32 was added and sonication was usedto dissolve it. The samples were applied to the back side of diffuser144 at a layer 60μ thick using a coating rod and irradiated once under HUV lamp at conveyor speed 2 m/min. Formulations 10 and 11 were preparedsimilarly to formulations 8 and 9, with respect to JK-71 and RS-106,respectively in place of JK-32.

Film 130 made from formulation 6 had a QY of 49%, emission peak at 615nm and a lifetime prolonging factor of x5 (see Table 1 for comparison tofilms 130 prepared by sol-gel processes). Film 130 made from formulation7 had a QY of 57%, emission peak at 616 nm and a lifetime prolongingfactor of x8. FIG. 13 illustrates the emission spectra of films 130produced from formulations 8-11, according to some embodiments of theinvention.

Formulations 6-9 and 11 are shown with red fluorescent RBF compounds andmay be used as red-enhancing films 130 in displays with white lightsource 80B. In some embodiments, green fluorescent RBF compounds may beadded to these formulations or may be applied in separate formulationsto form films added to red fluorescent films.

Formulation 10 is shown with green fluorescent RBF compounds and may beused as green-enhancing films 130. In some embodiments, red fluorescentRBF compounds may be added to this formulation or may be applied inseparate formulations to form films added to green fluorescent films.

Protective Films

Some embodiments comprise applying a protective film 131 to colorconversion film 130 and/or configuring color conversion film 130 to haveprotective properties which prevent humidity damages and cracking. Anytype of color conversion film 130 may be protected and/or enhanced asdescribed in the following, e.g., RBF-compounds-based films 130 as wellas films 130 based on other organic or inorganic fluorescent moleculesand quantum-dot-based color conversion films 130.

For example, UV cured protective film 131 may be formed using a mixtureof 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,triarylsulfonium hexafluoroantimonate salts, mixed-50 wt % in propylenecarbonate, polyether modified polydimethylsiloxane and3-ethyloxetane-3-methanol, which is UV cured on a conveyor.

In another example, UV cured protective film 131 may be formed by mixing76.8% 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 19.2%trimethylolpropane (TMP) oxetane (TMPO), 3.8% triarylsulfoniumhexafluoroantimonate salts, mixed-50 wt % in propylene carbonate and0.2% polyether-modified polydimethylsiloxane (in this order) andstirring the mixture at room temperature. The sample was applied to asol-gel layer (e.g., color conversion film 130 produced by a sol gelprocess disclosed above) by drawing using a coating rod to form a 50 μmlayer and then irradiated once under H UV lamp at conveyor speed 7m/min. The sol-gel layer was cleaned with ethanol and air dried beforecoating.

FIG. 14 is a high level flowchart illustrating a method 105, accordingto some embodiments of the invention. The stages of method 105 may becarried out with respect to various aspects of precursors 110,formulations 120, films 130 and displays 140 described above, which mayoptionally be configured to implement method 105, irrespective of theorder of the stages.

In some embodiments, method 105 comprises configuring a LCD with RGBcolor filters to have at least one color conversion film prepared tohave a R emission peak and/or a G emission peak (stage 150), patterningthe at least one color conversion film with respect to a patterning ofthe RGB color filters to yield a spatial correspondence between filmregions with R and G emission peaks and respective R and G color filter(stage 160), and positioning the color conversion film in an LCD panelof the LCD (stage 165).

In some embodiments, method 105 comprises configuring a LCD with RGBcolor filters to have at least one color conversion film prepared tohave a R emission peak and a G emission peak (stage 150), and adjustingan intensity of the R and G emission peaks of the at least one colorconversion film to fine tune a white point of the LCD to be at a centerof an expected line of deterioration of the intensity within given LCDspecifications (stage 170).

In some embodiments, method 105 comprises configuring a LCD with RGBcolor filters to have at least one color conversion film prepared tohave a R emission peak and a G emission peak (stage 150), preparing theat least one color conversion film using a matrix and a process whichdirect self-assembly of molecules of color conversion molecules of theat least one color conversion film to yield polarization of at leastpart of illumination emitted by the color conversion film (stage 180),and replacing at least one polarizer in the LCD by the at least onecolor conversion film (stage 185).

In some embodiments, method 105 comprises configuring a LCD with RGBcolor filters and white backlight illumination to have at least onecolor conversion film prepared to have a R emission peak (stage 190).

In some embodiments, method 105 further comprises applying a protectivelayer to the color conversion film (stage 195). For example, method 105may further comprise any of: preparing the protective layer by a sol gelprocess with at least one of: zirconium-phenyl siloxane hybrid material(ZPH), methyl methacrylate (MMA), trimethoxysilane derivative and anESOR; preparing the protective layer by an acetic anhydride surfacetreatment and/or a trimethylsilane surface treatment; and/or preparingthe protective layer by a UV curing process using a mixture of3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate andtriarylsulfonium hexafluoroantimonate salts, mixed in propylenecarbonate.

The at least one color conversion film may comprise at least one RBFcompound defined by Formula 1 and/or Formula 2.

In method 105, the at least one color conversion film may be prepared byat least one corresponding sol-gel process (stage and method 200) and/orUV curing process (stage and method 300), which are presented in moredetail below.

FIG. 14 is further a high-level flowchart illustrating a method 200which may be part of method 105, according to some embodiments of theinvention. The stages of method 200 may be carried out with respect tovarious aspects of precursors 110, formulations 120, films 130 anddisplays 140 described above, which may optionally be configured toimplement method 200. Method 200 may comprise stages for producing,preparing and/or using precursors 110, formulations 120, films 130 anddisplays 140, such as any of the following stages, irrespective of theirorder.

Method 200 may comprise preparing a hybrid sol-gel precursor formulationfrom: an ESOR prepared from TEOS, at least one MTMOS or TMOS derivative,and GLYMO; a DURS powder prepared from isocyanate-functionalized silicananoparticles and ethylene glycol; and a metal(s) alkoxide matrixsolution (stage 210), mixing the prepared hybrid sol-gel precursor withat least one RBF compound (stage 220); and spreading the mixture anddrying the spread mixture to form a film (stage 230).

Method 200 may comprise comprising evaporating alcohols from the mixtureprior to spreading 230 (stage 225). The inventors have found out thatusing ethylene glycol 108 in the preparation of DURS 109 and evaporating225 the alcohols prior to spreading improve film properties, and, forexample, enable reducing the number of required green-fluorescent RBFlayers 132 due to the increased viscosity of formulation 120. Possibly,the number of required green-fluorescent RBF layers 132 may be reducedto one by substantial or complete evaporation of the alcohols informulation 120 prior to spreading 230.

Preparing 210 of the hybrid sol-gel precursor formulation may be carriedout under acidic conditions (stage 212), mixing 220 may compriseadjusting types and amounts of the TMOS derivatives to tune emissionwavelengths of the fluorophores (stage 215), spreading and drying 230may be carried out respectively by bar coating and by at least one ofconvective heating, evaporating and infrared radiation (stage 240).

As explained above, the RBF compound may be a red-fluorescent RBFcompound and the TMOS derivative(s) may comprise for example PhTMOSand/or a TMOS with fluorine substituents; and/or the RBF compound may bea green-fluorescent RBF compound and the TMOS derivative(s) may comprisePhTMOS and/or F₁TMOS with the PhTMOS:F₁TMOS ratio being adjusted to tuneemission properties of the green-fluorescent RBF compound. Other TMOSderivatives may comprise F₂TMOS(tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane,1,2-bis(triethoxysilyl)ethane, trimethoxy(propyl)silane,octadecyltrimethoxysilane, fluorotriethoxysilane, andammonium(propyl)trimethoxysilane.

Method 200 may comprise forming the film from at least one redfluorescent RBF compound and/or from at least one green fluorescent RBFcompound (stage 250). The RBF compound(s) may be supramolecularyencapsulated and/or covalently embedded in one or more layers. Asnon-limiting examples, method 200 may comprise forming the film from atleast one red fluorescent RBF compound to enhance a red illuminationcomponent in displays using a white light source (stage 280), such as awhite-LED-based display. Alternatively or complementarily films may beformed to have both red and green fluorescent RBF compounds and be usedfor enhancing red and green illumination components in displays using ablue light source (blue LEDs).

Method 200 may comprise associating the film with any of the diffuser,prism film(s) and polarizer film(s) in a display backlight unit (stage260), e.g. attaching one or more films onto any of the elements in thedisplay backlight unit or possibly replacing one or more of theseelements by the formed film(s). For example, method 200 may compriseconfiguring the film to exhibit polarization properties (stage 270) andusing the polarizing film to enhance or replace polarizer film(s) in thedisplay backlight unit.

FIG. 14 is further a high level flowchart illustrating a method 300which may be part of method 105, according to some embodiments of theinvention. The stages of method 300 may be carried out with respect tovarious aspects of formulations 120, films 130 and displays 140described above, which may optionally be configured to implement method300. Method 300 may comprise stages for producing, preparing and/orusing formulations 120, films 130 and displays 140, such as any of thefollowing stages, irrespective of their order.

Method 300 may comprise preparing a formulation from 65-70% monomers,25-30% oligomers, 1-5% photointiator and at least one RBF compound(stage 310), in weight percentages of the total formulation, spreadingthe formulation to form a film (stage 330), and UV curing theformulation (stage 340). Method 300 may comprise any of: selecting themonomers from: dipropylene glycol diacrylate, ditrimethylolpropanetetraacrylate, dipentaerythritol hexaacrylate, ethoxylatedpentaerythritol tetraacrylate, propoxylated (3) glyceryl acrylate andtrimethylolpropane triacrylate; selecting the oligomers from: polyesteracrylate, modified polyester resin diluted with dipropyleneglycoldiacrylate and aliphatic urethane hexaacrylate; and selecting thephotointiator from: alpha-hydroxy-cyclohexyl-phenyl-ketone andalpha-hydroxy ketone (possibly difunctional).

Method 300 may further comprise configuring the formulation and the filmto yield a color conversion film and determining UV curing parameters toavoid damage to the color conversion elements, such as RBF compound(s)(stage 345). Method 300 may further comprise forming the colorconversion film with at least one red fluorescent RBF compound and withat least one green fluorescent RBF compound (stage 350).

In some embodiments, method 300 may comprise configuring the colorconversion film to exhibit polarization properties (stage 370), e.g., bydirecting self-assembly of molecules of the RBF compound(s) into atleast partial alignment. Method 300 may further comprise associating thecolor conversion film with any of: a diffuser, a prism film and apolarizer film in a display backlight unit (stage 360).

In some embodiments, method 300 may comprise forming the colorconversion film with at least one red fluorescent RBF compound toenhance a red illumination component in a white-LED-based display (stage380) by shifting some of the yellow region in the emission spectrum ofthe white light source into the red region, namely into the Rtransmission region of the R color filter, to reduce illumination lossesin the LCD panel while maintaining the balance between B and R+G regionsin the RGB illumination (stage 382).

Enhanced Fluorescence

Certain embodiments may utilize resonance effects to enhance thefluorescent properties of film 130 and of RBF compounds 115 in film 130,in particular to improve their performance in display 140. For example,RBF compounds 115 may be electromagnetically coupled with metallicnanoparticles and/or surfaces to increase quantum yields, increasephotostability, decrease distances for resonance energy transfer, andincrease lifetimes, to provide increased sensitivity and photostabilityand decrease interference from unwanted background emission. Forexample, the Purcell effect (electromagnetic coupling of the fluorescentmolecule with tightly confined high-density surface plasmon modes) andlocal surface plasmon resonance (LSPR) in plasmonic nanostructures andhyperbolic metamaterials may be used for these purposes, by providingrespective wavelength and spatial relations between RBF compounds 115and the metallic nanoparticles and/or surfaces.

FIGS. 15A and 15B are high level schematic illustrations fluorescentelements 111 comprising RBF compounds 115 coupled to plasmon-resonant(PR) elements 112, according to some embodiments of the invention. RBFcompounds 115 may be coupled to PR-elements 112 by various linkers 114,illustrated schematically. FIG. 15C is a high level schematic spectrumillustration with absorption and emission wavelengths 115A, 115B,respectively, of RBF compounds 115 and related local surface plasmonresonance (LSPR) properties 112A of various PR elements 112, accordingto some embodiments of the invention. PR elements 112 may be selected tocouple their LSPR with absorption and/or emission of RBF compounds 115,to enhance the latter.

PR elements 112 such as silver (Ag) and/or gold (Au) nanoparticles,coatings and shells may be used to enhance the photoluminescentproperties of RBF compounds 115 to provide metal-enhanced fluorescencewhich may be based on the local surface plasmon resonance (LSPR)properties of PR elements 112 such as the metals nanoparticles. Theinteractions of fluorescent compounds with metallic surfaces may enhancethe fluorescence by e.g., increasing the quantum yield, increasing thephotostability, decreasing the distances for resonance energy transfer,increasing the lifetime, increasing the sensitivity and photostabilityand/or decreasing the interference from unwanted background emissions influorescent elements 111 with respect to RBF compounds 115 which are notcoupled to PR-elements 112.

PR elements 112 may have various shapes and sizes. As non-limitingexamples, FIG. 15A illustrates round PR elements 112 and FIG. 15Billustrates square PR elements 112. Linkers 114 may be selected from awide range of molecules which may provide effective coupling of LSPR tothe fluorescence absorption and/or emission. In a non-limiting example,FIG. 15B illustrates cetyltrimethylammonium bromide ((C₁₆H₃₃)N(CH₃)₃Br,CTAB) as linker 114, having its N(CH₃)₃Br end denoted by 114A andbonding RBF compound 115 and PR element 112; and its (C₁₆H₃₃) enddenoted by 114B. In the illustrated non-limiting example, two layers ofCTAB are used to link RBF compound 115 and PR element 112. Otherexamples for linkers 114 may comprise short to large (e.g., 1-12aliphatic —CH₂— units) chemical linkers containing cationic surfactants(such as CTAB), thiol groups (e.g., mercapto silane based materials),carboxylic acid, sulfonic acid, phosphate acid groups such as mercaptopropionic acid up to undecanoic acid, or thioctic acid. For example,molar ratios of 1:1 to 1:100 of metal:chemical linker may be used inwater-based solutions, e.g., 10 ml of HAuCl₄ 2.0 mM may be mixed andcentrifuged with 375 μL of NaBH₄ 0.11 M in the presence of thioctic acid(TA) as a surfactant (100:1 Au:TA), followed by tuning of the pH to ca.8-9 using 0.1 M KOH solution, further centrifuging and re-dispersion inDI (deionized) water.

FIG. 15C schematically illustrates alternative or complementaryproperties of LSPR 112A of PR element 112 with respect to absorption andemission peaks 115A, 115B, respectively of RBF compound 115, namelypartial or full overlap between one or both absorption and emissionpeaks 115A, 115B and narrowband LSPR 112A, and/or partial overlapbetween absorption and emission peaks 115A, 115B and broadband LSPR112A. Any of these as well as intermediate situations may be configuredto provide the fluorescence enhancement by coupling LSPR 112A to peaks115A and/or 115B.

The relations between PR elements 112 and RBF compounds 115 may beconfigured with respect to any of the following parameters: the metallicmaterial, size and geometry of PR elements 112, the dielectricsurrounding of PR elements 112 and RBF compounds 115, and the spatialrelations and linkers 114 between PR elements 112 and RBF compounds 115.These may be configured to enhance the coupling between PR elements 112and RBF compounds 115 and promote constructive resonances between them.

FIG. 16 is a high level schematic illustration of film 130 having PRelements 112 as coating of enclosure of RBF compounds 115 embedded in amatrix 136, according to some embodiments of the invention. PR elements112 may be deposited upon film 130 produced as disclosed above as acontinuous coating, as islands as interconnected spots, or in any otherpattern, which provides coupling (indicated schematically by numeral114) between PR elements 112 and RBF compounds 115. For example,coupling 114 may be carried out through direct contact of RBF compounds115 with PR elements 112 and/or via matrix 136 which may comprise linkerelements as additives.

In some embodiments, matrix 136 may comprise for example as the sol-gelor UV cured matrixes disclosed above, or any other polymer or glassmatrix. Solid matrix 136 with embedded RBF compounds 115 may be coatedwith a plasmonic metallic thin film 112 such as gold or silver at athickness up to 100 nm, e.g., by metal evaporation or local reductionfrom a solution containing the metal salt precursor (such as goldchloride or silver nitrate) and a reducing agent (such as sodiumborohydride or ascorbic acid). Alternatively or complementarily, apowder of gold or silver nanoparticles at diameters of 10-100 nm may beadded to the compound-polymer blend (e.g., formulations 120) at a laststage of making the respective solid polymer/glass 136 with embedded RBFcompounds 115, before the final solidification (baking/curing).Thereafter the solidification/baking/curing step may be continued.

As a non-limiting example of a deposition method of PR elements 112 onfilm 130, the following was carried out. Glass substrate was cut andcleaned (e.g., using 1:3 H₂O₂:H₂SO₄ and/or 1:1:5 H₂O₂:NH₄OH:H₂O at 70°C. for 30 min, followed by washing, e.g., in water of methanol), andthen modified with a chemical linker such Aminopropyltriethoxysilane(APTS) by overnight immersion in a 10 v/% APTS solution in methanol. Thesilanized glass substrates was then sonicated three times in methanol,washed with ethanol and dried under a stream of nitrogen, and thentransferred to the evaporation chamber. Au evaporation on glass orsilicon substrates was carried out in a cryo-HV evaporator equipped witha thickness monitor. Homogeneous deposition was achieved by moderaterotation of the substrate plate. Au was evaporated from a tungsten boatat 2-4 μTorr. For preparation of Au island films on glass, a lowdeposition rate of 0.01 nm s⁻¹ was applied. Post-deposition annealing ofAu-covered slides was carried out in air at 200° C. for 20 h using anoven. The annealed substrates were left to cool in air to roomtemperature. The annealing temperature was chosen to maintain goodadhesion of the Au to the substrates, provided by the organic silanemonolayer.

FIG. 17 is a high level schematic illustration of film 130 having PRelements 112 as regular elements embedded in a film 118, to which RBFcompounds 115 are coupled, according to some embodiments of theinvention. PR elements 112 may be deposited using various methods, suchas disclosed above with respect to glass substrates and/or the sol gelor UV cured matrixes disclosed herein.

FIG. 18 is a high level schematic illustration of film 130 having PRelements 112 as regular perforations 112 in film 118, to which RBFcompounds 115 are coupled, according to some embodiments of theinvention. Perforations 112 in film 118 may be produced in varioustechnologies. For example, the following method yielded and array ofholes 112 of sizes under 500 nm with different LSPR wavelengths. Thinfilm 118 was (<100 nm) made by evaporated metal thin film on atransparent and flexible/rigid polymer, glass or quartz film 130 using amask by means of photolithography. Following the preparation ofmetal-hole film 118, it was coated with RBF compounds 115 by anevaporation method in a vacuum chamber (at 10⁻⁶ mbar), with a powder ofRBF compounds 115 inserted into the vacuum chamber and heated to100-200° C. to deposit the evaporated compounds on metal-hole thin film118, or alternatively by activating metal thin film 118 by deposition ofsimilar chemical linkers 114 as disclosed above to couple RBF compounds115 to perforations 112.

FIG. 19 is a high level schematic illustration of fluorescent elements111 having PR elements 112 as composite structures to which RBFcompounds 115 are coupled, according to some embodiments of theinvention. PR elements 112 may be implemented as multilayered hyperbolicmetamaterials having hyperbolic dispersion relations. For example,fluorescent elements 111 may comprise PR elements 112 as multilayershaving pairs of metallic and dielectric or semiconducting layers 112A,112B. For example, Ag—Si multilayers may be used, composed of 15 pairsof 10 nm Ag and 10 nm Si layers (112A, 112B) with a capping Si layer of5 nm, were prepared by alternately DC magnetron sputtering Si and Aglayers onto glass substrates 124 at room temperature. Sputtering ratesfor Ag and Si at 50 W (˜2.5 W cm⁻²) were 1.6 Å s⁻¹ and 0.16 Å s⁻¹. The 5nm capping layer helps to prevent Ag oxidation as well as rapidquenching of emitters in the vicinity of the metal surface. The basepressure of the chamber was 5×10⁻⁸ torr and the Ar pressure was fixed at2.0 mtorr. Nanoscale trenches (widths W) were inscribed into themultilayers by focused ion beam (FIB) milling with different periods toform grating nanostructures. RBF compounds 115 mixed in PMMA as matrix136 were spin-coated onto the uniform and nanopatterned surface of themultilayers to a thickness of 80 nm to form a flat polymethylmetacrylate(PMMA) top surface. Fluorescent elements 111 may be used as film 130 indisplay 140. The dimensions W (trench width), d (pitch of multilayeredstructure), H (height of multilayered structure) and h (thickness oflayer with RBF compounds 115) may be configured according to specificfilm and display performance requirements, types and density of RBFcompounds 115, film production method etc.

FIG. 20 is a high level flowchart illustrating a method 400, accordingto some embodiments of the invention. Method 400 may be part ofaforementioned methods 105, 200, 300. Method 400 may comprise couplingfluorescent compound(s) to plasmonic nanostructures to enhance thefluorescent emission (stage 210), e.g., using linkers for the coupling(stage 212). Method 400 may comprise enhancing the plasmon field bynanoparticle design (stage 214).

Method 400 may comprise embedding fluorescent compound(s) in a matrixenclosed within plasmonic nanostructure shells to enhance thefluorescent emission (stage 220). Method 400 may comprise couplingfluorescent compound(s) to plasmonic island nanostructures on atransparent film to enhance the fluorescent emission (stage 230). Method400 may comprise coupling fluorescent compound(s) to plasmonic hole(e.g., perforations) nanostructures on a transparent film to enhance thefluorescent emission (stage 240). Method 400 may comprise couplingfluorescent compound(s) to multilayered plasmonic nanostructures (suchas hyperbolic metamaterials) to enhance the fluorescent emission (stage250).

In the above description, an embodiment is an example or implementationof the invention. The various appearances of “one embodiment”, “anembodiment”, “certain embodiments” or “some embodiments” do notnecessarily all refer to the same embodiments. Although various featuresof the invention may be described in the context of a single embodiment,the features may also be provided separately or in any suitablecombination. Conversely, although the invention may be described hereinin the context of separate embodiments for clarity, the invention mayalso be implemented in a single embodiment. Certain embodiments of theinvention may include features from different embodiments disclosedabove, and certain embodiments may incorporate elements from otherembodiments disclosed above. The disclosure of elements of the inventionin the context of a specific embodiment is not to be taken as limitingtheir use in the specific embodiment alone. Furthermore, it is to beunderstood that the invention can be carried out or practiced in variousways and that the invention can be implemented in certain embodimentsother than the ones outlined in the description above.

The invention is not limited to those diagrams or to the correspondingdescriptions. For example, flow need not move through each illustratedbox or state, or in exactly the same order as illustrated and described.Meanings of technical and scientific terms used herein are to becommonly understood as by one of ordinary skill in the art to which theinvention belongs, unless otherwise defined. While the invention hasbeen described with respect to a limited number of embodiments, theseshould not be construed as limitations on the scope of the invention,but rather as exemplifications of some of the preferred embodiments.Other possible variations, modifications, and applications are alsowithin the scope of the invention. Accordingly, the scope of theinvention should not be limited by what has thus far been described, butby the appended claims and their legal equivalents.

The invention claimed is:
 1. A color conversion film for a LCD (liquidcrystal display) having RGB (red, green, blue) color filters, the colorconversion film comprising at least one rhodamine-based fluorescent(RBF) compound selected to absorb illumination from a backlight sourceof the LCD and having at least one of a R emission peak and a G emissionpeak, wherein the at least one RBF compound is defined by Formula 1:

wherein: R¹ is COOR, NO₂, COR, COSR, CO(N-heterocycle), CON(R)₂, or CN;R² each is independently selected from H, halide, N(R)₂, COR, CN,CON(R)₂, CO(N-heterocycle), NCO, NCS, OR, SR, SO₃H, SO₃M and COOR; R³each is independently selected from H, halide, N(R)₂, COR, CN, CON(R)₂,CO(N-heterocycle), NCO, NCS, OR, SR, SO₃H, SO₃M and COOR; R⁴-R¹⁶ andR^(4′)-R^(16′) are each independently selected from H, CF₃, alkyl,haloalkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl, benzyl,halide, NO₂, OR, N(R)₂, COR, CN, CON(R)₂, CO(N-Heterocycle) and COOR; Ris H, alkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl,benzyl, —(CH₂CH₂O)_(r)CH₂CH₂OH, —(CH₂)_(p)OC(O)NH(CH₂)_(q)Si(Oalkyl)₃,—(CH₂)_(p)OC(O)CH═CH₂ or —(CH₂)_(p)Si(Oalkyl)₃; n and m is eachindependently an integer between 1-4; p and q are each independently aninteger between 1-6; r is an integer between 0-10; M is a monovalentcation; and X is an anion; and wherein at least some of the at least oneRBF compound is electromagnetically coupled to plasmon-resonant (PR)elements having a resonance spectrum that at least partly overlap atleast one of an absorption and an emission spectra of the at least oneRBF compound, wherein the PR elements comprise metallic nanoparticlesranging in diameter between 10-100 nm, metal coated or sputtered on thecolor conversion film, a metallic film comprising islands orperforations on at least part of the color conversion film, a multilayerhyperbolic metamaterial, or a combination thereof.
 2. The colorconversion film according to claim 1, wherein the PR elements aremetallic nanoparticles ranging in diameter between 10-100 nm.
 3. Thecolor conversion film of claim 1, wherein the PR elements are coated orsputtered on the color conversion film.
 4. The color conversion film ofclaim 1, wherein the PR elements are islands or perforations on at leastpart of the color conversion film.
 5. The color conversion film of claim1, wherein the PR elements are configured as a hyperbolic metamaterial.6. The color conversion film of claim 1, produced at least partially bya sol gel process and/or a UV (ultraviolet) curing process.
 7. The LCDcomprising the color conversion film of claim
 1. 8. A method comprising:preparing at least one color conversion film comprising at least one RBFcompound selected to absorb illumination from a backlight source of theLCD and having at least one of a R emission peak and a G emission peak,wherein the at least one RBF compound is defined by Formula I:

wherein: R¹ is COOR, NO₂, COR, COSR, CO(N-heterocycle), CON(R)₂, or CN;R² each is independently selected from H, halide, N(R)₂, COR, CN,CON(R)₂, CO(N-heterocycle), NCO, NCS, OR, SR, SO₃H, SO₃M and COOR; R³each is independently selected from H, halide, N(R)₂, COR, CN, CON(R)₂,CO(N-heterocycle), NCO, NCS, OR, SR, SO₃H, SO₃M and COOR; R⁴-R¹⁶ andR^(4′)-R^(16′) are each independently selected from H, CF3, alkyl,haloalkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl, benzyl,halide, NO₂, OR, N(R)₂, COR, CN, CON(R)₂, CO(N-Heterocycle) and COOR; Ris H, alkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl,benzyl, —(CH₂CH₂O)_(r)CH₂CH₂OH, —(CH₂)_(p)OC(O)NH(CH₂)_(q)Si(Oalkyl)₃,—(CH₂)_(p)OC(O)CH═CH₂ or —(CH₂)_(p)Si(Oalkyl)₃; n and m is eachindependently an integer between 1-4; p and q are each independently aninteger between 1-6; r is an integer between 0-10; M is a monovalentcation; and X is an anion; electromagnetically coupling at least some ofthe at least one RBF compound to PR elements having a resonance spectrumthat at least partly overlap at least one of an absorption and anemission spectra of the at least one RBF compound, wherein the PRelements comprise metallic nanoparticles ranging in diameter between10-100 nm, metal coated or sputtered on the color conversion film, ametallic film comprising islands or perforations on at least part of thecolor conversion film, a multilayer hyperbolic metamaterial, or acombination thereof, and integrating the at least one color conversionfilm in a LCD with RGB color filters.
 9. The method of claim 8, furthercomprising using linkers for the electromagnetic coupling.
 10. Themethod of claim 8, further comprising designing PR elements to enhance aplasmon field thereof.
 11. The method of claim 8, further comprisingembedding the at least one RBF compound in a matrix enclosed within thePR elements being plasmonic nanostructure shells.
 12. The method ofclaim 8, further comprising coating or sputtering the PR elements on theat least one color conversion film.
 13. The method of claim 8, whereinthe at least one color conversion film is prepared by at least onecorresponding sol-gel process and/or UV curing process.